diff options
59 files changed, 3486 insertions, 166 deletions
@@ -1,5 +1,5 @@ -Libpng 1.2.44 - June 26, 2010 +Libpng 1.2.46 - July 9, 2011 This is a public release of libpng, intended for use in production codes. @@ -8,48 +8,56 @@ Files available for download: Source files with LF line endings (for Unix/Linux) and with a "configure" script - libpng-1.2.44.tar.xz (LZMA-compressed, recommended) - libpng-1.2.44.tar.gz - libpng-1.2.44.tar.bz2 + libpng-1.2.46.tar.xz (LZMA-compressed, recommended) + libpng-1.2.46.tar.gz + libpng-1.2.46.tar.bz2 Source files with LF line endings (for Unix/Linux) without the "configure" script - libpng-1.2.44-no-config.tar.xz (LZMA-compressed, recommended) - libpng-1.2.44-no-config.tar.gz - libpng-1.2.44-no-config.tar.bz2 + libpng-1.2.46-no-config.tar.xz (LZMA-compressed, recommended) + libpng-1.2.46-no-config.tar.gz + libpng-1.2.46-no-config.tar.bz2 Source files with CRLF line endings (for Windows), without the "configure" script - lpng1244.zip - lpng1244.7z - lpng1244.tar.bz2 + lpng1246.zip + lpng1246.7z + lpng1246.tar.bz2 Project files - libpng-1.2.44-project-netware.zip - libpng-1.2.44-project-wince.zip + libpng-1.2.46-project-netware.zip + libpng-1.2.46-project-wince.zip Other information: - libpng-1.2.44-README.txt - libpng-1.2.44-KNOWNBUGS.txt - libpng-1.2.44-LICENSE.txt - libpng-1.2.44-Y2K-compliance.txt - libpng-1.2.44-[previous version]-diff.txt + libpng-1.2.46-README.txt + libpng-1.2.46-KNOWNBUGS.txt + libpng-1.2.46-LICENSE.txt + libpng-1.2.46-Y2K-compliance.txt + libpng-1.2.46-[previous version]-diff.txt Changes since the last public release (1.2.43): -version 1.2.44 [June 26, 2010] - - Rewrote png_process_IDAT_data to consistently treat extra data as warnings - and handle end conditions more cleanly. - Removed the now-redundant check for out-of-bounds new_row from example.c - +version 1.2.45 [July 9, 2011] + + Fixed uninitialized memory read in png_format_buffer() (Bug + report by Frank Busse, related to CVE-2004-0421). + Pass "" instead of '\0' to png_default_error() in png_err(). This mistake + was introduced in libpng-1.2.20beta01. + Check for up->location !PNG_AFTER_IDAT when writing unknown chunks + before IDAT. + Ported bugfix in pngrtran.c from 1.5.3: when expanding a paletted image, + always expand to RGBA if transparency is present. + Check for integer overflow in png_set_rgb_to_gray(). + Check for sCAL chunk too short. + Added CMakeLists.txt, projects/xcode, and pnggccrd.c to EXTRA_DIST in + Makefile.am and Makefile.in + Udated copyright year to 2011. Send comments/corrections/commendations to png-mng-implement at lists.sf.net - (subscription required; visit https://lists.sourceforge.net/lists/listinfo/png-mng-implement to subscribe) or to glennrp at users.sourceforge.net @@ -1478,7 +1478,7 @@ version 1.2.9beta5 [March 4, 2006] Removed trailing blanks from source files. Put version and date of latest change in each source file, and changed copyright year accordingly. - More cleanup of configure.ac, Makefile.ac, and associated scripts. + More cleanup of configure.ac, Makefile.am, and associated scripts. Restored scripts/makefile.elf which was inadvertently deleted. version 1.2.9beta6 [March 6, 2006] @@ -2704,6 +2704,38 @@ version 1.2.44rc03 [June 23, 2010] version 1.2.44 [June 26, 2010] Updated some of the "last changed" dates. +version 1.2.45beta01 [June 7, 2011] + Fixed uninitialized memory read in png_format_buffer() (Bug + report by Frank Busse, related to CVE-2004-0421). + Pass "" instead of '\0' to png_default_error() in png_err(). This mistake + was introduced in libpng-1.2.20beta01. + Check for up->location !PNG_AFTER_IDAT when writing unknown chunks + before IDAT. + Ported bugfix in pngrtran.c from 1.5.3: when expanding a paletted image, + always expand to RGBA if transparency is present. + +version 1.2.45beta02 [June 8, 2011] + Check for integer overflow in png_set_rgb_to_gray(). + +version 1.2.45beta03 [June 19, 2011] + Check for sCAL chunk too short. + +version 1.2.45rc01 and 1.0.55rc01 [June 30, 2011] + Updated "last changed" dates and copyright year. + +version 1.2.45 and 1.0.55 [July 7, 2011] + No changes. + +version 1.2.46rc01 and 1.0.56rc01 [July 8, 2011] + Reverted changes to Makefile.am and Makefile.in to libpng-1.2.44 versions. + +version 1.2.46rc02 and 1.0.56rc02 [July 8, 2011] + Added CMakeLists.txt, projects/xcode, and pnggccrd.c to EXTRA_DIST in + Makefile.am and Makefile.in + +version 1.2.46 and 1.0.56 [July 9, 2011] + Udated copyright year to 2011. + Send comments/corrections/commendations to png-mng-implement at lists.sf.net (subscription required; visit https://lists.sourceforge.net/lists/listinfo/png-mng-implement diff --git a/CMakeLists.txt b/CMakeLists.txt index ebe66cc..a3ab464 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -22,7 +22,7 @@ enable_testing() set(PNGLIB_MAJOR 1) set(PNGLIB_MINOR 2) -set(PNGLIB_RELEASE 44) +set(PNGLIB_RELEASE 46) set(PNGLIB_NAME libpng${PNGLIB_MAJOR}${PNGLIB_MINOR}) set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_RELEASE}) @@ -215,7 +215,7 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/libpng-config.in # SET UP LINKS if(PNG_SHARED) set_target_properties(${PNG_LIB_NAME} PROPERTIES -# VERSION 0.${PNGLIB_RELEASE}.1.2.44 +# VERSION 0.${PNGLIB_RELEASE}.1.2.46 VERSION 0.${PNGLIB_RELEASE}.0 SOVERSION 0 CLEAN_DIRECT_OUTPUT 1) @@ -1,5 +1,5 @@ -Installing libpng version 1.2.44 - June 26, 2010 +Installing libpng version 1.2.46 - July 9, 2011 On Unix/Linux and similar systems, you can simply type @@ -46,7 +46,7 @@ to have access to the zlib.h and zconf.h include files that correspond to the version of zlib that's installed. You can rename the directories that you downloaded (they -might be called "libpng-1.2.44" or "libpng12" and "zlib-1.2.3" +might be called "libpng-1.2.46" or "libpng12" and "zlib-1.2.3" or "zlib123") so that you have directories called "zlib" and "libpng". Your directory structure should look like this: @@ -1,24 +1,17 @@ -Known bugs in libpng version 1.2.44 +Known bugs in libpng version 1.2.46 -1. December 4, 2009: The PNG_NO_ERROR_NUMBERS macro was inadvertently - defined in libpng-1.2.41/pngconf.h, which may cause a problem with - building a binary-compatible library. - - STATUS: This will be fixed in libpng-1.2.42. In the meantime, simply - delete the definition from line : - -2. February 23, 2006: The custom makefiles don't build libpng with -lz. +1. February 23, 2006: The custom makefiles don't build libpng with -lz. STATUS: This is a subject of debate. The change will probably be made as a part of a major overhaul of the makefiles in libpng version 1.4.0. -3. February 24, 2006: The Makefile generated by the "configure" script +2. February 24, 2006: The Makefile generated by the "configure" script fails to install symbolic links libpng12.so => libpng12.so.0.1.2.9betaN that are generated by the custom makefiles. -4. September 4, 2007: There is a report that pngtest crashes on MacOS 10. +3. September 4, 2007: There is a report that pngtest crashes on MacOS 10. STATUS: workarounds are 1) Compile without optimization (crashes are observed with @@ -10,7 +10,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.2.44, June 26, 2010, are +libpng versions 1.2.6, August 15, 2004, through 1.2.46, July 9, 2011, are Copyright (c) 2004, 2006-2009 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -108,4 +108,4 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -June 26, 2010 +July 9, 2011 diff --git a/Makefile.am b/Makefile.am index 17051cd..d3289ca 100644 --- a/Makefile.am +++ b/Makefile.am @@ -74,19 +74,22 @@ pkgconfig_DATA = libpng12.pc EXTRA_DIST= \ ANNOUNCE CHANGES INSTALL KNOWNBUG LICENSE README TODO Y2KINFO \ pngtest.png pngbar.png pngnow.png pngbar.jpg autogen.sh \ + CMakeLists.txt \ ${srcdir}/projects/cbuilder5/* \ ${srcdir}/projects/beos/* \ ${srcdir}/projects/visualc6/* \ ${srcdir}/projects/visualc71/* \ ${srcdir}/projects/wince.txt \ ${srcdir}/projects/netware.txt \ + ${srcdir}/projects/xcode/* \ ${srcdir}/scripts/* \ ${srcdir}/contrib/gregbook/* \ + ${srcdir}/contrib/pngminim/* \ ${srcdir}/contrib/pngminus/* \ ${srcdir}/contrib/pngsuite/* \ ${srcdir}/contrib/visupng/* \ $(TESTS) \ - example.c libpng-1.2.44.txt pngvcrd.c + example.c libpng-1.2.46.txt pnggccrd.c pngvcrd.c CLEANFILES= pngout.png libpng12.pc libpng12-config libpng.vers \ libpng.sym diff --git a/Makefile.in b/Makefile.in index b9c41f0..d07cb3d 100644 --- a/Makefile.in +++ b/Makefile.in @@ -338,20 +338,23 @@ pkgconfig_DATA = libpng12.pc #extra source distribution files. EXTRA_DIST = \ ANNOUNCE CHANGES INSTALL KNOWNBUG LICENSE README TODO Y2KINFO \ + CMakeLists.txt \ pngtest.png pngbar.png pngnow.png pngbar.jpg autogen.sh \ ${srcdir}/projects/cbuilder5/* \ ${srcdir}/projects/beos/* \ ${srcdir}/projects/visualc6/* \ ${srcdir}/projects/visualc71/* \ ${srcdir}/projects/wince.txt \ + ${srcdir}/projects/xcode/* \ ${srcdir}/projects/netware.txt \ ${srcdir}/scripts/* \ ${srcdir}/contrib/gregbook/* \ + ${srcdir}/contrib/pngminim/* \ ${srcdir}/contrib/pngminus/* \ ${srcdir}/contrib/pngsuite/* \ ${srcdir}/contrib/visupng/* \ $(TESTS) \ - example.c libpng-1.2.44.txt pngvcrd.c + example.c libpng-1.2.46.txt pnggccrd.c pngvcrd.c CLEANFILES = pngout.png libpng12.pc libpng12-config libpng.vers \ libpng.sym @@ -8,8 +8,10 @@ COPYRIGHT NOTICE, DISCLAIMER, and LICENSE: If you modify libpng you may insert additional notices immediately following this sentence. -libpng versions 1.2.6, August 15, 2004, through 1.2.29, May 8, 2008, are -Copyright (c) 2004, 2006-2008 Glenn Randers-Pehrson, and are +This code is released under the libpng license. + +libpng versions 1.2.6, August 15, 2004, through 1.2.46, July 9, 2011, are +Copyright (c) 2004, 2006-2009 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -106,4 +108,4 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -May 8, 2008 +July 9, 2011 @@ -1,4 +1,4 @@ -README for libpng version 1.2.44 - June 26, 2010 (shared library 12.0) +README for libpng version 1.2.46 - July 9, 2011 (shared library 12.0) See the note about version numbers near the top of png.h See INSTALL for instructions on how to install libpng. @@ -199,11 +199,11 @@ Files in this distribution: makefile.std => Generic UNIX makefile (cc, creates static libpng.a) makefile.elf => Linux/ELF gcc makefile symbol versioning, - creates libpng12.so.0.1.2.44) + creates libpng12.so.0.1.2.46) makefile.linux => Linux/ELF makefile (gcc, creates - libpng12.so.0.1.2.44) + libpng12.so.0.1.2.46) makefile.gcmmx => Linux/ELF makefile (gcc, creates - libpng12.so.0.1.2.44, previously + libpng12.so.0.1.2.46, previously used assembler code tuned for Intel MMX platform) makefile.gcc => Generic makefile (gcc, creates static @@ -228,12 +228,12 @@ Files in this distribution: makefile.openbsd => OpenBSD makefile makefile.sgi => Silicon Graphics IRIX (cc, creates static lib) makefile.sggcc => Silicon Graphics - (gcc, creates libpng12.so.0.1.2.44) + (gcc, creates libpng12.so.0.1.2.46) makefile.sunos => Sun makefile makefile.solaris => Solaris 2.X makefile - (gcc, creates libpng12.so.0.1.2.44) + (gcc, creates libpng12.so.0.1.2.46) makefile.so9 => Solaris 9 makefile - (gcc, creates libpng12.so.0.1.2.44) + (gcc, creates libpng12.so.0.1.2.46) makefile.32sunu => Sun Ultra 32-bit makefile makefile.64sunu => Sun Ultra 64-bit makefile makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc @@ -1,13 +1,13 @@ Y2K compliance in libpng: ========================= - June 26, 2010 + July 9, 2011 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. This is your unofficial assurance that libpng from version 0.71 and - upward through 1.2.44 are Y2K compliant. It is my belief that earlier + upward through 1.2.46 are Y2K compliant. It is my belief that earlier versions were also Y2K compliant. Libpng only has three year fields. One is a 2-byte unsigned integer @@ -1,6 +1,6 @@ #! /bin/sh # Guess values for system-dependent variables and create Makefiles. -# Generated by GNU Autoconf 2.65 for libpng 1.2.44. +# Generated by GNU Autoconf 2.65 for libpng 1.2.46. # # Report bugs to <png-mng-implement@lists.sourceforge.net>. # @@ -701,8 +701,8 @@ MAKEFLAGS= # Identity of this package. PACKAGE_NAME='libpng' PACKAGE_TARNAME='libpng' -PACKAGE_VERSION='1.2.44' -PACKAGE_STRING='libpng 1.2.44' +PACKAGE_VERSION='1.2.46' +PACKAGE_STRING='libpng 1.2.46' PACKAGE_BUGREPORT='png-mng-implement@lists.sourceforge.net' PACKAGE_URL='' @@ -1435,7 +1435,7 @@ if test "$ac_init_help" = "long"; then # Omit some internal or obsolete options to make the list less imposing. # This message is too long to be a string in the A/UX 3.1 sh. cat <<_ACEOF -\`configure' configures libpng 1.2.44 to adapt to many kinds of systems. +\`configure' configures libpng 1.2.46 to adapt to many kinds of systems. Usage: $0 [OPTION]... [VAR=VALUE]... @@ -1505,7 +1505,7 @@ fi if test -n "$ac_init_help"; then case $ac_init_help in - short | recursive ) echo "Configuration of libpng 1.2.44:";; + short | recursive ) echo "Configuration of libpng 1.2.46:";; esac cat <<\_ACEOF @@ -1612,7 +1612,7 @@ fi test -n "$ac_init_help" && exit $ac_status if $ac_init_version; then cat <<\_ACEOF -libpng configure 1.2.44 +libpng configure 1.2.46 generated by GNU Autoconf 2.65 Copyright (C) 2009 Free Software Foundation, Inc. @@ -2037,7 +2037,7 @@ cat >config.log <<_ACEOF This file contains any messages produced by compilers while running configure, to aid debugging if configure makes a mistake. -It was created by libpng $as_me 1.2.44, which was +It was created by libpng $as_me 1.2.46, which was generated by GNU Autoconf 2.65. Invocation command line was $ $0 $@ @@ -2845,7 +2845,7 @@ fi # Define the identity of the package. PACKAGE='libpng' - VERSION='1.2.44' + VERSION='1.2.46' cat >>confdefs.h <<_ACEOF @@ -2909,10 +2909,10 @@ fi -PNGLIB_VERSION=1.2.44 +PNGLIB_VERSION=1.2.46 PNGLIB_MAJOR=1 PNGLIB_MINOR=2 -PNGLIB_RELEASE=44 +PNGLIB_RELEASE=46 @@ -12079,7 +12079,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1 # report actual input values of CONFIG_FILES etc. instead of their # values after options handling. ac_log=" -This file was extended by libpng $as_me 1.2.44, which was +This file was extended by libpng $as_me 1.2.46, which was generated by GNU Autoconf 2.65. Invocation command line was CONFIG_FILES = $CONFIG_FILES @@ -12145,7 +12145,7 @@ _ACEOF cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`" ac_cs_version="\\ -libpng config.status 1.2.44 +libpng config.status 1.2.46 configured by $0, generated by GNU Autoconf 2.65, with options \\"\$ac_cs_config\\" diff --git a/configure.ac b/configure.ac index c624a74..bfdbf7a 100644 --- a/configure.ac +++ b/configure.ac @@ -18,15 +18,15 @@ AC_PREREQ(2.59) dnl Version number stuff here: -AC_INIT([libpng], [1.2.44], [png-mng-implement@lists.sourceforge.net]) +AC_INIT([libpng], [1.2.46], [png-mng-implement@lists.sourceforge.net]) AM_INIT_AUTOMAKE dnl stop configure from automagically running automake AM_MAINTAINER_MODE -PNGLIB_VERSION=1.2.44 +PNGLIB_VERSION=1.2.46 PNGLIB_MAJOR=1 PNGLIB_MINOR=2 -PNGLIB_RELEASE=44 +PNGLIB_RELEASE=46 dnl End of version number stuff diff --git a/libpng-1.2.46.txt b/libpng-1.2.46.txt new file mode 100644 index 0000000..9edd7aa --- /dev/null +++ b/libpng-1.2.46.txt @@ -0,0 +1,3234 @@ +libpng.txt - A description on how to use and modify libpng + + libpng version 1.2.46 - July 9, 2011 + Updated and distributed by Glenn Randers-Pehrson + <glennrp at users.sourceforge.net> + Copyright (c) 1998-2009 Glenn Randers-Pehrson + + This document is released under the libpng license. + For conditions of distribution and use, see the disclaimer + and license in png.h + + Based on: + + libpng versions 0.97, January 1998, through 1.2.46 - July 9, 2011 + Updated and distributed by Glenn Randers-Pehrson + Copyright (c) 1998-2009 Glenn Randers-Pehrson + + libpng 1.0 beta 6 version 0.96 May 28, 1997 + Updated and distributed by Andreas Dilger + Copyright (c) 1996, 1997 Andreas Dilger + + libpng 1.0 beta 2 - version 0.88 January 26, 1996 + For conditions of distribution and use, see copyright + notice in png.h. Copyright (c) 1995, 1996 Guy Eric + Schalnat, Group 42, Inc. + + Updated/rewritten per request in the libpng FAQ + Copyright (c) 1995, 1996 Frank J. T. Wojcik + December 18, 1995 & January 20, 1996 + +I. Introduction + +This file describes how to use and modify the PNG reference library +(known as libpng) for your own use. There are five sections to this +file: introduction, structures, reading, writing, and modification and +configuration notes for various special platforms. In addition to this +file, example.c is a good starting point for using the library, as +it is heavily commented and should include everything most people +will need. We assume that libpng is already installed; see the +INSTALL file for instructions on how to install libpng. + +For examples of libpng usage, see the files "example.c", "pngtest.c", +and the files in the "contrib" directory, all of which are included in +the libpng distribution. + +Libpng was written as a companion to the PNG specification, as a way +of reducing the amount of time and effort it takes to support the PNG +file format in application programs. + +The PNG specification (second edition), November 2003, is available as +a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at +<http://www.w3.org/TR/2003/REC-PNG-20031110/ +The W3C and ISO documents have identical technical content. + +The PNG-1.2 specification is available at +<http://www.libpng.org/pub/png/documents/>. It is technically equivalent +to the PNG specification (second edition) but has some additional material. + +The PNG-1.0 specification is available +as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a +W3C Recommendation <http://www.w3.org/TR/REC.png.html>. + +Some additional chunks are described in the special-purpose public chunks +documents at <http://www.libpng.org/pub/png/documents/>. + +Other information +about PNG, and the latest version of libpng, can be found at the PNG home +page, <http://www.libpng.org/pub/png/>. + +Most users will not have to modify the library significantly; advanced +users may want to modify it more. All attempts were made to make it as +complete as possible, while keeping the code easy to understand. +Currently, this library only supports C. Support for other languages +is being considered. + +Libpng has been designed to handle multiple sessions at one time, +to be easily modifiable, to be portable to the vast majority of +machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy +to use. The ultimate goal of libpng is to promote the acceptance of +the PNG file format in whatever way possible. While there is still +work to be done (see the TODO file), libpng should cover the +majority of the needs of its users. + +Libpng uses zlib for its compression and decompression of PNG files. +Further information about zlib, and the latest version of zlib, can +be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>. +The zlib compression utility is a general purpose utility that is +useful for more than PNG files, and can be used without libpng. +See the documentation delivered with zlib for more details. +You can usually find the source files for the zlib utility wherever you +find the libpng source files. + +Libpng is thread safe, provided the threads are using different +instances of the structures. Each thread should have its own +png_struct and png_info instances, and thus its own image. +Libpng does not protect itself against two threads using the +same instance of a structure. + +II. Structures + +There are two main structures that are important to libpng, png_struct +and png_info. The first, png_struct, is an internal structure that +will not, for the most part, be used by a user except as the first +variable passed to every libpng function call. + +The png_info structure is designed to provide information about the +PNG file. At one time, the fields of png_info were intended to be +directly accessible to the user. However, this tended to cause problems +with applications using dynamically loaded libraries, and as a result +a set of interface functions for png_info (the png_get_*() and png_set_*() +functions) was developed. The fields of png_info are still available for +older applications, but it is suggested that applications use the new +interfaces if at all possible. + +Applications that do make direct access to the members of png_struct (except +for png_ptr->jmpbuf) must be recompiled whenever the library is updated, +and applications that make direct access to the members of png_info must +be recompiled if they were compiled or loaded with libpng version 1.0.6, +in which the members were in a different order. In version 1.0.7, the +members of the png_info structure reverted to the old order, as they were +in versions 0.97c through 1.0.5. Starting with version 2.0.0, both +structures are going to be hidden, and the contents of the structures will +only be accessible through the png_get/png_set functions. + +The png.h header file is an invaluable reference for programming with libpng. +And while I'm on the topic, make sure you include the libpng header file: + +#include <png.h> + +III. Reading + +We'll now walk you through the possible functions to call when reading +in a PNG file sequentially, briefly explaining the syntax and purpose +of each one. See example.c and png.h for more detail. While +progressive reading is covered in the next section, you will still +need some of the functions discussed in this section to read a PNG +file. + +Setup + +You will want to do the I/O initialization(*) before you get into libpng, +so if it doesn't work, you don't have much to undo. Of course, you +will also want to insure that you are, in fact, dealing with a PNG +file. Libpng provides a simple check to see if a file is a PNG file. +To use it, pass in the first 1 to 8 bytes of the file to the function +png_sig_cmp(), and it will return 0 (false) if the bytes match the +corresponding bytes of the PNG signature, or nonzero (true) otherwise. +Of course, the more bytes you pass in, the greater the accuracy of the +prediction. + +If you are intending to keep the file pointer open for use in libpng, +you must ensure you don't read more than 8 bytes from the beginning +of the file, and you also have to make a call to png_set_sig_bytes_read() +with the number of bytes you read from the beginning. Libpng will +then only check the bytes (if any) that your program didn't read. + +(*): If you are not using the standard I/O functions, you will need +to replace them with custom functions. See the discussion under +Customizing libpng. + + + FILE *fp = fopen(file_name, "rb"); + if (!fp) + { + return (ERROR); + } + fread(header, 1, number, fp); + is_png = !png_sig_cmp(header, 0, number); + if (!is_png) + { + return (NOT_PNG); + } + + +Next, png_struct and png_info need to be allocated and initialized. In +order to ensure that the size of these structures is correct even with a +dynamically linked libpng, there are functions to initialize and +allocate the structures. We also pass the library version, optional +pointers to error handling functions, and a pointer to a data struct for +use by the error functions, if necessary (the pointer and functions can +be NULL if the default error handlers are to be used). See the section +on Changes to Libpng below regarding the old initialization functions. +The structure allocation functions quietly return NULL if they fail to +create the structure, so your application should check for that. + + png_structp png_ptr = png_create_read_struct + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + user_error_fn, user_warning_fn); + if (!png_ptr) + return (ERROR); + + png_infop info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) + { + png_destroy_read_struct(&png_ptr, + (png_infopp)NULL, (png_infopp)NULL); + return (ERROR); + } + + png_infop end_info = png_create_info_struct(png_ptr); + if (!end_info) + { + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); + } + +If you want to use your own memory allocation routines, +define PNG_USER_MEM_SUPPORTED and use +png_create_read_struct_2() instead of png_create_read_struct(): + + png_structp png_ptr = png_create_read_struct_2 + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + user_error_fn, user_warning_fn, (png_voidp) + user_mem_ptr, user_malloc_fn, user_free_fn); + +The error handling routines passed to png_create_read_struct() +and the memory alloc/free routines passed to png_create_struct_2() +are only necessary if you are not using the libpng supplied error +handling and memory alloc/free functions. + +When libpng encounters an error, it expects to longjmp back +to your routine. Therefore, you will need to call setjmp and pass +your png_jmpbuf(png_ptr). If you read the file from different +routines, you will need to update the jmpbuf field every time you enter +a new routine that will call a png_*() function. + +See your documentation of setjmp/longjmp for your compiler for more +information on setjmp/longjmp. See the discussion on libpng error +handling in the Customizing Libpng section below for more information +on the libpng error handling. If an error occurs, and libpng longjmp's +back to your setjmp, you will want to call png_destroy_read_struct() to +free any memory. + + if (setjmp(png_jmpbuf(png_ptr))) + { + png_destroy_read_struct(&png_ptr, &info_ptr, + &end_info); + fclose(fp); + return (ERROR); + } + +If you would rather avoid the complexity of setjmp/longjmp issues, +you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +errors will result in a call to PNG_ABORT() which defaults to abort(). + +Now you need to set up the input code. The default for libpng is to +use the C function fread(). If you use this, you will need to pass a +valid FILE * in the function png_init_io(). Be sure that the file is +opened in binary mode. If you wish to handle reading data in another +way, you need not call the png_init_io() function, but you must then +implement the libpng I/O methods discussed in the Customizing Libpng +section below. + + png_init_io(png_ptr, fp); + +If you had previously opened the file and read any of the signature from +the beginning in order to see if this was a PNG file, you need to let +libpng know that there are some bytes missing from the start of the file. + + png_set_sig_bytes(png_ptr, number); + +Setting up callback code + +You can set up a callback function to handle any unknown chunks in the +input stream. You must supply the function + + read_chunk_callback(png_ptr ptr, + png_unknown_chunkp chunk); + { + /* The unknown chunk structure contains your + chunk data, along with similar data for any other + unknown chunks: */ + + png_byte name[5]; + png_byte *data; + png_size_t size; + + /* Note that libpng has already taken care of + the CRC handling */ + + /* put your code here. Search for your chunk in the + unknown chunk structure, process it, and return one + of the following: */ + + return (-n); /* chunk had an error */ + return (0); /* did not recognize */ + return (n); /* success */ + } + +(You can give your function another name that you like instead of +"read_chunk_callback") + +To inform libpng about your function, use + + png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr, + read_chunk_callback); + +This names not only the callback function, but also a user pointer that +you can retrieve with + + png_get_user_chunk_ptr(png_ptr); + +If you call the png_set_read_user_chunk_fn() function, then all unknown +chunks will be saved when read, in case your callback function will need +one or more of them. This behavior can be changed with the +png_set_keep_unknown_chunks() function, described below. + +At this point, you can set up a callback function that will be +called after each row has been read, which you can use to control +a progress meter or the like. It's demonstrated in pngtest.c. +You must supply a function + + void read_row_callback(png_ptr ptr, png_uint_32 row, + int pass); + { + /* put your code here */ + } + +(You can give it another name that you like instead of "read_row_callback") + +To inform libpng about your function, use + + png_set_read_status_fn(png_ptr, read_row_callback); + +Unknown-chunk handling + +Now you get to set the way the library processes unknown chunks in the +input PNG stream. Both known and unknown chunks will be read. Normal +behavior is that known chunks will be parsed into information in +various info_ptr members while unknown chunks will be discarded. This +behavior can be wasteful if your application will never use some known +chunk types. To change this, you can call: + + png_set_keep_unknown_chunks(png_ptr, keep, + chunk_list, num_chunks); + keep - 0: default unknown chunk handling + 1: ignore; do not keep + 2: keep only if safe-to-copy + 3: keep even if unsafe-to-copy + You can use these definitions: + PNG_HANDLE_CHUNK_AS_DEFAULT 0 + PNG_HANDLE_CHUNK_NEVER 1 + PNG_HANDLE_CHUNK_IF_SAFE 2 + PNG_HANDLE_CHUNK_ALWAYS 3 + chunk_list - list of chunks affected (a byte string, + five bytes per chunk, NULL or '\0' if + num_chunks is 0) + num_chunks - number of chunks affected; if 0, all + unknown chunks are affected. If nonzero, + only the chunks in the list are affected + +Unknown chunks declared in this way will be saved as raw data onto a +list of png_unknown_chunk structures. If a chunk that is normally +known to libpng is named in the list, it will be handled as unknown, +according to the "keep" directive. If a chunk is named in successive +instances of png_set_keep_unknown_chunks(), the final instance will +take precedence. The IHDR and IEND chunks should not be named in +chunk_list; if they are, libpng will process them normally anyway. + +Here is an example of the usage of png_set_keep_unknown_chunks(), +where the private "vpAg" chunk will later be processed by a user chunk +callback function: + + png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'}; + + #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) + png_byte unused_chunks[]= + { + 104, 73, 83, 84, (png_byte) '\0', /* hIST */ + 105, 84, 88, 116, (png_byte) '\0', /* iTXt */ + 112, 67, 65, 76, (png_byte) '\0', /* pCAL */ + 115, 67, 65, 76, (png_byte) '\0', /* sCAL */ + 115, 80, 76, 84, (png_byte) '\0', /* sPLT */ + 116, 73, 77, 69, (png_byte) '\0', /* tIME */ + }; + #endif + + ... + + #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) + /* ignore all unknown chunks: */ + png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); + /* except for vpAg: */ + png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); + /* also ignore unused known chunks: */ + png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, + (int)sizeof(unused_chunks)/5); + #endif + +User limits + +The PNG specification allows the width and height of an image to be as +large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns. +Since very few applications really need to process such large images, +we have imposed an arbitrary 1-million limit on rows and columns. +Larger images will be rejected immediately with a png_error() call. If +you wish to override this limit, you can use + + png_set_user_limits(png_ptr, width_max, height_max); + +to set your own limits, or use width_max = height_max = 0x7fffffffL +to allow all valid dimensions (libpng may reject some very large images +anyway because of potential buffer overflow conditions). + +You should put this statement after you create the PNG structure and +before calling png_read_info(), png_read_png(), or png_process_data(). +If you need to retrieve the limits that are being applied, use + + width_max = png_get_user_width_max(png_ptr); + height_max = png_get_user_height_max(png_ptr); + +The PNG specification sets no limit on the number of ancillary chunks +allowed in a PNG datastream. You can impose a limit on the total number +of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with + + png_set_chunk_cache_max(png_ptr, user_chunk_cache_max); + +where 0x7fffffffL means unlimited. You can retrieve this limit with + + chunk_cache_max = png_get_chunk_cache_max(png_ptr); + +This limit also applies to the number of buffers that can be allocated +by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks. + +The high-level read interface + +At this point there are two ways to proceed; through the high-level +read interface, or through a sequence of low-level read operations. +You can use the high-level interface if (a) you are willing to read +the entire image into memory, and (b) the input transformations +you want to do are limited to the following set: + + PNG_TRANSFORM_IDENTITY No transformation + PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to + 8 bits + PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel + PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit + samples to bytes + PNG_TRANSFORM_PACKSWAP Change order of packed + pixels to LSB first + PNG_TRANSFORM_EXPAND Perform set_expand() + PNG_TRANSFORM_INVERT_MONO Invert monochrome images + PNG_TRANSFORM_SHIFT Normalize pixels to the + sBIT depth + PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA + to BGRA + PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA + to AG + PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity + to transparency + PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples + PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples + to RGB (or GA to RGBA) + +(This excludes setting a background color, doing gamma transformation, +dithering, and setting filler.) If this is the case, simply do this: + + png_read_png(png_ptr, info_ptr, png_transforms, NULL) + +where png_transforms is an integer containing the bitwise OR of some +set of transformation flags. This call is equivalent to png_read_info(), +followed the set of transformations indicated by the transform mask, +then png_read_image(), and finally png_read_end(). + +(The final parameter of this call is not yet used. Someday it might point +to transformation parameters required by some future input transform.) + +You must use png_transforms and not call any png_set_transform() functions +when you use png_read_png(). + +After you have called png_read_png(), you can retrieve the image data +with + + row_pointers = png_get_rows(png_ptr, info_ptr); + +where row_pointers is an array of pointers to the pixel data for each row: + + png_bytep row_pointers[height]; + +If you know your image size and pixel size ahead of time, you can allocate +row_pointers prior to calling png_read_png() with + + if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) + png_error (png_ptr, + "Image is too tall to process in memory"); + if (width > PNG_UINT_32_MAX/pixel_size) + png_error (png_ptr, + "Image is too wide to process in memory"); + row_pointers = png_malloc(png_ptr, + height*png_sizeof(png_bytep)); + for (int i=0; i<height, i++) + row_pointers[i]=NULL; /* security precaution */ + for (int i=0; i<height, i++) + row_pointers[i]=png_malloc(png_ptr, + width*pixel_size); + png_set_rows(png_ptr, info_ptr, &row_pointers); + +Alternatively you could allocate your image in one big block and define +row_pointers[i] to point into the proper places in your block. + +If you use png_set_rows(), the application is responsible for freeing +row_pointers (and row_pointers[i], if they were separately allocated). + +If you don't allocate row_pointers ahead of time, png_read_png() will +do it, and it'll be free'ed when you call png_destroy_*(). + +The low-level read interface + +If you are going the low-level route, you are now ready to read all +the file information up to the actual image data. You do this with a +call to png_read_info(). + + png_read_info(png_ptr, info_ptr); + +This will process all chunks up to but not including the image data. + +Querying the info structure + +Functions are used to get the information from the info_ptr once it +has been read. Note that these fields may not be completely filled +in until png_read_end() has read the chunk data following the image. + + png_get_IHDR(png_ptr, info_ptr, &width, &height, + &bit_depth, &color_type, &interlace_type, + &compression_type, &filter_method); + + width - holds the width of the image + in pixels (up to 2^31). + height - holds the height of the image + in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the + image channels. (valid values are + 1, 2, 4, 8, 16 and depend also on + the color_type. See also + significant bits (sBIT) below). + color_type - describes which color/alpha channels + are present. + PNG_COLOR_TYPE_GRAY + (bit depths 1, 2, 4, 8, 16) + PNG_COLOR_TYPE_GRAY_ALPHA + (bit depths 8, 16) + PNG_COLOR_TYPE_PALETTE + (bit depths 1, 2, 4, 8) + PNG_COLOR_TYPE_RGB + (bit_depths 8, 16) + PNG_COLOR_TYPE_RGB_ALPHA + (bit_depths 8, 16) + + PNG_COLOR_MASK_PALETTE + PNG_COLOR_MASK_COLOR + PNG_COLOR_MASK_ALPHA + + filter_method - (must be PNG_FILTER_TYPE_BASE + for PNG 1.0, and can also be + PNG_INTRAPIXEL_DIFFERENCING if + the PNG datastream is embedded in + a MNG-1.0 datastream) + compression_type - (must be PNG_COMPRESSION_TYPE_BASE + for PNG 1.0) + interlace_type - (PNG_INTERLACE_NONE or + PNG_INTERLACE_ADAM7) + + Any or all of interlace_type, compression_type, or + filter_method can be NULL if you are + not interested in their values. + + Note that png_get_IHDR() returns 32-bit data into + the application's width and height variables. + This is an unsafe situation if these are 16-bit + variables. In such situations, the + png_get_image_width() and png_get_image_height() + functions described below are safer. + + width = png_get_image_width(png_ptr, + info_ptr); + height = png_get_image_height(png_ptr, + info_ptr); + bit_depth = png_get_bit_depth(png_ptr, + info_ptr); + color_type = png_get_color_type(png_ptr, + info_ptr); + filter_method = png_get_filter_type(png_ptr, + info_ptr); + compression_type = png_get_compression_type(png_ptr, + info_ptr); + interlace_type = png_get_interlace_type(png_ptr, + info_ptr); + + channels = png_get_channels(png_ptr, info_ptr); + channels - number of channels of info for the + color type (valid values are 1 (GRAY, + PALETTE), 2 (GRAY_ALPHA), 3 (RGB), + 4 (RGB_ALPHA or RGB + filler byte)) + rowbytes = png_get_rowbytes(png_ptr, info_ptr); + rowbytes - number of bytes needed to hold a row + + signature = png_get_signature(png_ptr, info_ptr); + signature - holds the signature read from the + file (if any). The data is kept in + the same offset it would be if the + whole signature were read (i.e. if an + application had already read in 4 + bytes of signature before starting + libpng, the remaining 4 bytes would + be in signature[4] through signature[7] + (see png_set_sig_bytes())). + +These are also important, but their validity depends on whether the chunk +has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and +png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the +data has been read, or zero if it is missing. The parameters to the +png_get_<chunk> are set directly if they are simple data types, or a +pointer into the info_ptr is returned for any complex types. + + png_get_PLTE(png_ptr, info_ptr, &palette, + &num_palette); + palette - the palette for the file + (array of png_color) + num_palette - number of entries in the palette + + png_get_gAMA(png_ptr, info_ptr, &gamma); + gamma - the gamma the file is written + at (PNG_INFO_gAMA) + + png_get_sRGB(png_ptr, info_ptr, &srgb_intent); + srgb_intent - the rendering intent (PNG_INFO_sRGB) + The presence of the sRGB chunk + means that the pixel data is in the + sRGB color space. This chunk also + implies specific values of gAMA and + cHRM. + + png_get_iCCP(png_ptr, info_ptr, &name, + &compression_type, &profile, &proflen); + name - The profile name. + compression - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + profile - International Color Consortium color + profile data. May contain NULs. + proflen - length of profile data in bytes. + + png_get_sBIT(png_ptr, info_ptr, &sig_bit); + sig_bit - the number of significant bits for + (PNG_INFO_sBIT) each of the gray, + red, green, and blue channels, + whichever are appropriate for the + given color type (png_color_16) + + png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, + &trans_values); + trans - array of transparent + entries for palette (PNG_INFO_tRNS) + trans_values - graylevel or color sample values of + the single transparent color for + non-paletted images (PNG_INFO_tRNS) + num_trans - number of transparent entries + (PNG_INFO_tRNS) + + png_get_hIST(png_ptr, info_ptr, &hist); + (PNG_INFO_hIST) + hist - histogram of palette (array of + png_uint_16) + + png_get_tIME(png_ptr, info_ptr, &mod_time); + mod_time - time image was last modified + (PNG_VALID_tIME) + + png_get_bKGD(png_ptr, info_ptr, &background); + background - background color (PNG_VALID_bKGD) + valid 16-bit red, green and blue + values, regardless of color_type + + num_comments = png_get_text(png_ptr, info_ptr, + &text_ptr, &num_text); + num_comments - number of comments + text_ptr - array of png_text holding image + comments + text_ptr[i].compression - type of compression used + on "text" PNG_TEXT_COMPRESSION_NONE + PNG_TEXT_COMPRESSION_zTXt + PNG_ITXT_COMPRESSION_NONE + PNG_ITXT_COMPRESSION_zTXt + text_ptr[i].key - keyword for comment. Must contain + 1-79 characters. + text_ptr[i].text - text comments for current + keyword. Can be empty. + text_ptr[i].text_length - length of text string, + after decompression, 0 for iTXt + text_ptr[i].itxt_length - length of itxt string, + after decompression, 0 for tEXt/zTXt + text_ptr[i].lang - language of comment (empty + string for unknown). + text_ptr[i].lang_key - keyword in UTF-8 + (empty string for unknown). + Note that the itxt_length, lang, and lang_key + members of the text_ptr structure only exist + when the library is built with iTXt chunk support. + + num_text - number of comments (same as + num_comments; you can put NULL here + to avoid the duplication) + Note while png_set_text() will accept text, language, + and translated keywords that can be NULL pointers, the + structure returned by png_get_text will always contain + regular zero-terminated C strings. They might be + empty strings but they will never be NULL pointers. + + num_spalettes = png_get_sPLT(png_ptr, info_ptr, + &palette_ptr); + palette_ptr - array of palette structures holding + contents of one or more sPLT chunks + read. + num_spalettes - number of sPLT chunks read. + + png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, + &unit_type); + offset_x - positive offset from the left edge + of the screen + offset_y - positive offset from the top edge + of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER + + png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, + &unit_type); + res_x - pixels/unit physical resolution in + x direction + res_y - pixels/unit physical resolution in + x direction + unit_type - PNG_RESOLUTION_UNKNOWN, + PNG_RESOLUTION_METER + + png_get_sCAL(png_ptr, info_ptr, &unit, &width, + &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units + (width and height are doubles) + + png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, + &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units + (width and height are strings like "2.54") + + num_unknown_chunks = png_get_unknown_chunks(png_ptr, + info_ptr, &unknowns) + unknowns - array of png_unknown_chunk + structures holding unknown chunks + unknowns[i].name - name of unknown chunk + unknowns[i].data - data of unknown chunk + unknowns[i].size - size of unknown chunk's data + unknowns[i].location - position of chunk in file + + The value of "i" corresponds to the order in which the + chunks were read from the PNG file or inserted with the + png_set_unknown_chunks() function. + +The data from the pHYs chunk can be retrieved in several convenient +forms: + + res_x = png_get_x_pixels_per_meter(png_ptr, + info_ptr) + res_y = png_get_y_pixels_per_meter(png_ptr, + info_ptr) + res_x_and_y = png_get_pixels_per_meter(png_ptr, + info_ptr) + res_x = png_get_x_pixels_per_inch(png_ptr, + info_ptr) + res_y = png_get_y_pixels_per_inch(png_ptr, + info_ptr) + res_x_and_y = png_get_pixels_per_inch(png_ptr, + info_ptr) + aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, + info_ptr) + + (Each of these returns 0 [signifying "unknown"] if + the data is not present or if res_x is 0; + res_x_and_y is 0 if res_x != res_y) + +The data from the oFFs chunk can be retrieved in several convenient +forms: + + x_offset = png_get_x_offset_microns(png_ptr, info_ptr); + y_offset = png_get_y_offset_microns(png_ptr, info_ptr); + x_offset = png_get_x_offset_inches(png_ptr, info_ptr); + y_offset = png_get_y_offset_inches(png_ptr, info_ptr); + + (Each of these returns 0 [signifying "unknown" if both + x and y are 0] if the data is not present or if the + chunk is present but the unit is the pixel) + +For more information, see the png_info definition in png.h and the +PNG specification for chunk contents. Be careful with trusting +rowbytes, as some of the transformations could increase the space +needed to hold a row (expand, filler, gray_to_rgb, etc.). +See png_read_update_info(), below. + +A quick word about text_ptr and num_text. PNG stores comments in +keyword/text pairs, one pair per chunk, with no limit on the number +of text chunks, and a 2^31 byte limit on their size. While there are +suggested keywords, there is no requirement to restrict the use to these +strings. It is strongly suggested that keywords and text be sensible +to humans (that's the point), so don't use abbreviations. Non-printing +symbols are not allowed. See the PNG specification for more details. +There is also no requirement to have text after the keyword. + +Keywords should be limited to 79 Latin-1 characters without leading or +trailing spaces, but non-consecutive spaces are allowed within the +keyword. It is possible to have the same keyword any number of times. +The text_ptr is an array of png_text structures, each holding a +pointer to a language string, a pointer to a keyword and a pointer to +a text string. The text string, language code, and translated +keyword may be empty or NULL pointers. The keyword/text +pairs are put into the array in the order that they are received. +However, some or all of the text chunks may be after the image, so, to +make sure you have read all the text chunks, don't mess with these +until after you read the stuff after the image. This will be +mentioned again below in the discussion that goes with png_read_end(). + +Input transformations + +After you've read the header information, you can set up the library +to handle any special transformations of the image data. The various +ways to transform the data will be described in the order that they +should occur. This is important, as some of these change the color +type and/or bit depth of the data, and some others only work on +certain color types and bit depths. Even though each transformation +checks to see if it has data that it can do something with, you should +make sure to only enable a transformation if it will be valid for the +data. For example, don't swap red and blue on grayscale data. + +The colors used for the background and transparency values should be +supplied in the same format/depth as the current image data. They +are stored in the same format/depth as the image data in a bKGD or tRNS +chunk, so this is what libpng expects for this data. The colors are +transformed to keep in sync with the image data when an application +calls the png_read_update_info() routine (see below). + +Data will be decoded into the supplied row buffers packed into bytes +unless the library has been told to transform it into another format. +For example, 4 bit/pixel paletted or grayscale data will be returned +2 pixels/byte with the leftmost pixel in the high-order bits of the +byte, unless png_set_packing() is called. 8-bit RGB data will be stored +in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() +is called to insert filler bytes, either before or after each RGB triplet. +16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant +byte of the color value first, unless png_set_strip_16() is called to +transform it to regular RGB RGB triplets, or png_set_filler() or +png_set_add alpha() is called to insert filler bytes, either before or +after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can +be modified with +png_set_filler(), png_set_add_alpha(), or png_set_strip_16(). + +The following code transforms grayscale images of less than 8 to 8 bits, +changes paletted images to RGB, and adds a full alpha channel if there is +transparency information in a tRNS chunk. This is most useful on +grayscale images with bit depths of 2 or 4 or if there is a multiple-image +viewing application that wishes to treat all images in the same way. + + if (color_type == PNG_COLOR_TYPE_PALETTE) + png_set_palette_to_rgb(png_ptr); + + if (color_type == PNG_COLOR_TYPE_GRAY && + bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); + + if (png_get_valid(png_ptr, info_ptr, + PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); + +These three functions are actually aliases for png_set_expand(), added +in libpng version 1.0.4, with the function names expanded to improve code +readability. In some future version they may actually do different +things. + +As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was +added. It expands the sample depth without changing tRNS to alpha. + +As of libpng version 1.2.46, not all possible expansions are supported. + +In the following table, the 01 means grayscale with depth<8, 31 means +indexed with depth<8, other numerals represent the color type, "T" means +the tRNS chunk is present, A means an alpha channel is present, and O +means tRNS or alpha is present but all pixels in the image are opaque. + + FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O + TO + 01 - + 31 - + 0 1 - + 0T - + 0O - + 2 GX - + 2T - + 2O - + 3 1 - + 3T - + 3O - + 4A T - + 4O - + 6A GX TX TX - + 6O GX TX - + +Within the matrix, + "-" means the transformation is not supported. + "X" means the transformation is obtained by png_set_expand(). + "1" means the transformation is obtained by + png_set_expand_gray_1_2_4_to_8 + "G" means the transformation is obtained by + png_set_gray_to_rgb(). + "P" means the transformation is obtained by + png_set_expand_palette_to_rgb(). + "T" means the transformation is obtained by + png_set_tRNS_to_alpha(). + +PNG can have files with 16 bits per channel. If you only can handle +8 bits per channel, this will strip the pixels down to 8 bit. + + if (bit_depth == 16) + png_set_strip_16(png_ptr); + +If, for some reason, you don't need the alpha channel on an image, +and you want to remove it rather than combining it with the background +(but the image author certainly had in mind that you *would* combine +it with the background, so that's what you should probably do): + + if (color_type & PNG_COLOR_MASK_ALPHA) + png_set_strip_alpha(png_ptr); + +In PNG files, the alpha channel in an image +is the level of opacity. If you need the alpha channel in an image to +be the level of transparency instead of opacity, you can invert the +alpha channel (or the tRNS chunk data) after it's read, so that 0 is +fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit +images) is fully transparent, with + + png_set_invert_alpha(png_ptr); + +The PNG format only supports pixels with postmultiplied alpha. +If you want to replace the pixels, after reading them, with pixels +that have premultiplied color samples, you can do this with + + png_set_premultiply_alpha(png_ptr); + +If you do this, any input with a tRNS chunk will be expanded to +have an alpha channel. + +PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as +they can, resulting in, for example, 8 pixels per byte for 1 bit +files. This code expands to 1 pixel per byte without changing the +values of the pixels: + + if (bit_depth < 8) + png_set_packing(png_ptr); + +PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels +stored in a PNG image have been "scaled" or "shifted" up to the next +higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] +to 8 bits/sample in the range [0, 255]). However, it is also possible +to convert the PNG pixel data back to the original bit depth of the +image. This call reduces the pixels back down to the original bit depth: + + png_color_8p sig_bit; + + if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) + png_set_shift(png_ptr, sig_bit); + +PNG files store 3-color pixels in red, green, blue order. This code +changes the storage of the pixels to blue, green, red: + + if (color_type == PNG_COLOR_TYPE_RGB || + color_type == PNG_COLOR_TYPE_RGB_ALPHA) + png_set_bgr(png_ptr); + +PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them +into 4 or 8 bytes for windowing systems that need them in this format: + + if (color_type == PNG_COLOR_TYPE_RGB) + png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); + +where "filler" is the 8 or 16-bit number to fill with, and the location is +either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether +you want the filler before the RGB or after. This transformation +does not affect images that already have full alpha channels. To add an +opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which +will generate RGBA pixels. + +Note that png_set_filler() does not change the color type. If you want +to do that, you can add a true alpha channel with + + if (color_type == PNG_COLOR_TYPE_RGB || + color_type == PNG_COLOR_TYPE_GRAY) + png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); + +where "filler" contains the alpha value to assign to each pixel. +This function was added in libpng-1.2.7. + +If you are reading an image with an alpha channel, and you need the +data as ARGB instead of the normal PNG format RGBA: + + if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) + png_set_swap_alpha(png_ptr); + +For some uses, you may want a grayscale image to be represented as +RGB. This code will do that conversion: + + if (color_type == PNG_COLOR_TYPE_GRAY || + color_type == PNG_COLOR_TYPE_GRAY_ALPHA) + png_set_gray_to_rgb(png_ptr); + +Conversely, you can convert an RGB or RGBA image to grayscale or grayscale +with alpha. + + if (color_type == PNG_COLOR_TYPE_RGB || + color_type == PNG_COLOR_TYPE_RGB_ALPHA) + png_set_rgb_to_gray_fixed(png_ptr, error_action, + int red_weight, int green_weight); + + error_action = 1: silently do the conversion + error_action = 2: issue a warning if the original + image has any pixel where + red != green or red != blue + error_action = 3: issue an error and abort the + conversion if the original + image has any pixel where + red != green or red != blue + + red_weight: weight of red component times 100000 + green_weight: weight of green component times 100000 + If either weight is negative, default + weights (21268, 71514) are used. + +If you have set error_action = 1 or 2, you can +later check whether the image really was gray, after processing +the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. +It will return a png_byte that is zero if the image was gray or +1 if there were any non-gray pixels. bKGD and sBIT data +will be silently converted to grayscale, using the green channel +data, regardless of the error_action setting. + +With red_weight+green_weight<=100000, +the normalized graylevel is computed: + + int rw = red_weight * 65536; + int gw = green_weight * 65536; + int bw = 65536 - (rw + gw); + gray = (rw*red + gw*green + bw*blue)/65536; + +The default values approximate those recommended in the Charles +Poynton's Color FAQ, <http://www.inforamp.net/~poynton/> +Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net> + + Y = 0.212671 * R + 0.715160 * G + 0.072169 * B + +Libpng approximates this with + + Y = 0.21268 * R + 0.7151 * G + 0.07217 * B + +which can be expressed with integers as + + Y = (6969 * R + 23434 * G + 2365 * B)/32768 + +The calculation is done in a linear colorspace, if the image gamma +is known. + +If you have a grayscale and you are using png_set_expand_depth(), +png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to +a higher bit-depth, you must either supply the background color as a gray +value at the original file bit-depth (need_expand = 1) or else supply the +background color as an RGB triplet at the final, expanded bit depth +(need_expand = 0). Similarly, if you are reading a paletted image, you +must either supply the background color as a palette index (need_expand = 1) +or as an RGB triplet that may or may not be in the palette (need_expand = 0). + + png_color_16 my_background; + png_color_16p image_background; + + if (png_get_bKGD(png_ptr, info_ptr, &image_background)) + png_set_background(png_ptr, image_background, + PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); + else + png_set_background(png_ptr, &my_background, + PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); + +The png_set_background() function tells libpng to composite images +with alpha or simple transparency against the supplied background +color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), +you may use this color, or supply another color more suitable for +the current display (e.g., the background color from a web page). You +need to tell libpng whether the color is in the gamma space of the +display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file +(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one +that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't +know why anyone would use this, but it's here). + +To properly display PNG images on any kind of system, the application needs +to know what the display gamma is. Ideally, the user will know this, and +the application will allow them to set it. One method of allowing the user +to set the display gamma separately for each system is to check for a +SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be +correctly set. + +Note that display_gamma is the overall gamma correction required to produce +pleasing results, which depends on the lighting conditions in the surrounding +environment. In a dim or brightly lit room, no compensation other than +the physical gamma exponent of the monitor is needed, while in a dark room +a slightly smaller exponent is better. + + double gamma, screen_gamma; + + if (/* We have a user-defined screen + gamma value */) + { + screen_gamma = user_defined_screen_gamma; + } + /* One way that applications can share the same + screen gamma value */ + else if ((gamma_str = getenv("SCREEN_GAMMA")) + != NULL) + { + screen_gamma = (double)atof(gamma_str); + } + /* If we don't have another value */ + else + { + screen_gamma = 2.2; /* A good guess for a + PC monitor in a bright office or a dim room */ + screen_gamma = 2.0; /* A good guess for a + PC monitor in a dark room */ + screen_gamma = 1.7 or 1.0; /* A good + guess for Mac systems */ + } + +The png_set_gamma() function handles gamma transformations of the data. +Pass both the file gamma and the current screen_gamma. If the file does +not have a gamma value, you can pass one anyway if you have an idea what +it is (usually 0.45455 is a good guess for GIF images on PCs). Note +that file gammas are inverted from screen gammas. See the discussions +on gamma in the PNG specification for an excellent description of what +gamma is, and why all applications should support it. It is strongly +recommended that PNG viewers support gamma correction. + + if (png_get_gAMA(png_ptr, info_ptr, &gamma)) + png_set_gamma(png_ptr, screen_gamma, gamma); + else + png_set_gamma(png_ptr, screen_gamma, 0.45455); + +If you need to reduce an RGB file to a paletted file, or if a paletted +file has more entries then will fit on your screen, png_set_dither() +will do that. Note that this is a simple match dither that merely +finds the closest color available. This should work fairly well with +optimized palettes, and fairly badly with linear color cubes. If you +pass a palette that is larger then maximum_colors, the file will +reduce the number of colors in the palette so it will fit into +maximum_colors. If there is a histogram, it will use it to make +more intelligent choices when reducing the palette. If there is no +histogram, it may not do as good a job. + + if (color_type & PNG_COLOR_MASK_COLOR) + { + if (png_get_valid(png_ptr, info_ptr, + PNG_INFO_PLTE)) + { + png_uint_16p histogram = NULL; + + png_get_hIST(png_ptr, info_ptr, + &histogram); + png_set_dither(png_ptr, palette, num_palette, + max_screen_colors, histogram, 1); + } + else + { + png_color std_color_cube[MAX_SCREEN_COLORS] = + { ... colors ... }; + + png_set_dither(png_ptr, std_color_cube, + MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, + NULL,0); + } + } + +PNG files describe monochrome as black being zero and white being one. +The following code will reverse this (make black be one and white be +zero): + + if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY) + png_set_invert_mono(png_ptr); + +This function can also be used to invert grayscale and gray-alpha images: + + if (color_type == PNG_COLOR_TYPE_GRAY || + color_type == PNG_COLOR_TYPE_GRAY_ALPHA) + png_set_invert_mono(png_ptr); + +PNG files store 16 bit pixels in network byte order (big-endian, +ie. most significant bits first). This code changes the storage to the +other way (little-endian, i.e. least significant bits first, the +way PCs store them): + + if (bit_depth == 16) + png_set_swap(png_ptr); + +If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you +need to change the order the pixels are packed into bytes, you can use: + + if (bit_depth < 8) + png_set_packswap(png_ptr); + +Finally, you can write your own transformation function if none of +the existing ones meets your needs. This is done by setting a callback +with + + png_set_read_user_transform_fn(png_ptr, + read_transform_fn); + +You must supply the function + + void read_transform_fn(png_ptr ptr, row_info_ptr + row_info, png_bytep data) + +See pngtest.c for a working example. Your function will be called +after all of the other transformations have been processed. + +You can also set up a pointer to a user structure for use by your +callback function, and you can inform libpng that your transform +function will change the number of channels or bit depth with the +function + + png_set_user_transform_info(png_ptr, user_ptr, + user_depth, user_channels); + +The user's application, not libpng, is responsible for allocating and +freeing any memory required for the user structure. + +You can retrieve the pointer via the function +png_get_user_transform_ptr(). For example: + + voidp read_user_transform_ptr = + png_get_user_transform_ptr(png_ptr); + +The last thing to handle is interlacing; this is covered in detail below, +but you must call the function here if you want libpng to handle expansion +of the interlaced image. + + number_of_passes = png_set_interlace_handling(png_ptr); + +After setting the transformations, libpng can update your png_info +structure to reflect any transformations you've requested with this +call. This is most useful to update the info structure's rowbytes +field so you can use it to allocate your image memory. This function +will also update your palette with the correct screen_gamma and +background if these have been given with the calls above. + + png_read_update_info(png_ptr, info_ptr); + +After you call png_read_update_info(), you can allocate any +memory you need to hold the image. The row data is simply +raw byte data for all forms of images. As the actual allocation +varies among applications, no example will be given. If you +are allocating one large chunk, you will need to build an +array of pointers to each row, as it will be needed for some +of the functions below. + +Reading image data + +After you've allocated memory, you can read the image data. +The simplest way to do this is in one function call. If you are +allocating enough memory to hold the whole image, you can just +call png_read_image() and libpng will read in all the image data +and put it in the memory area supplied. You will need to pass in +an array of pointers to each row. + +This function automatically handles interlacing, so you don't need +to call png_set_interlace_handling() or call this function multiple +times, or any of that other stuff necessary with png_read_rows(). + + png_read_image(png_ptr, row_pointers); + +where row_pointers is: + + png_bytep row_pointers[height]; + +You can point to void or char or whatever you use for pixels. + +If you don't want to read in the whole image at once, you can +use png_read_rows() instead. If there is no interlacing (check +interlace_type == PNG_INTERLACE_NONE), this is simple: + + png_read_rows(png_ptr, row_pointers, NULL, + number_of_rows); + +where row_pointers is the same as in the png_read_image() call. + +If you are doing this just one row at a time, you can do this with +a single row_pointer instead of an array of row_pointers: + + png_bytep row_pointer = row; + png_read_row(png_ptr, row_pointer, NULL); + +If the file is interlaced (interlace_type != 0 in the IHDR chunk), things +get somewhat harder. The only current (PNG Specification version 1.2) +interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7) +is a somewhat complicated 2D interlace scheme, known as Adam7, that +breaks down an image into seven smaller images of varying size, based +on an 8x8 grid. + +libpng can fill out those images or it can give them to you "as is". +If you want them filled out, there are two ways to do that. The one +mentioned in the PNG specification is to expand each pixel to cover +those pixels that have not been read yet (the "rectangle" method). +This results in a blocky image for the first pass, which gradually +smooths out as more pixels are read. The other method is the "sparkle" +method, where pixels are drawn only in their final locations, with the +rest of the image remaining whatever colors they were initialized to +before the start of the read. The first method usually looks better, +but tends to be slower, as there are more pixels to put in the rows. + +If you don't want libpng to handle the interlacing details, just call +png_read_rows() seven times to read in all seven images. Each of the +images is a valid image by itself, or they can all be combined on an +8x8 grid to form a single image (although if you intend to combine them +you would be far better off using the libpng interlace handling). + +The first pass will return an image 1/8 as wide as the entire image +(every 8th column starting in column 0) and 1/8 as high as the original +(every 8th row starting in row 0), the second will be 1/8 as wide +(starting in column 4) and 1/8 as high (also starting in row 0). The +third pass will be 1/4 as wide (every 4th pixel starting in column 0) and +1/8 as high (every 8th row starting in row 4), and the fourth pass will +be 1/4 as wide and 1/4 as high (every 4th column starting in column 2, +and every 4th row starting in row 0). The fifth pass will return an +image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2), +while the sixth pass will be 1/2 as wide and 1/2 as high as the original +(starting in column 1 and row 0). The seventh and final pass will be as +wide as the original, and 1/2 as high, containing all of the odd +numbered scanlines. Phew! + +If you want libpng to expand the images, call this before calling +png_start_read_image() or png_read_update_info(): + + if (interlace_type == PNG_INTERLACE_ADAM7) + number_of_passes + = png_set_interlace_handling(png_ptr); + +This will return the number of passes needed. Currently, this +is seven, but may change if another interlace type is added. +This function can be called even if the file is not interlaced, +where it will return one pass. + +If you are not going to display the image after each pass, but are +going to wait until the entire image is read in, use the sparkle +effect. This effect is faster and the end result of either method +is exactly the same. If you are planning on displaying the image +after each pass, the "rectangle" effect is generally considered the +better looking one. + +If you only want the "sparkle" effect, just call png_read_rows() as +normal, with the third parameter NULL. Make sure you make pass over +the image number_of_passes times, and you don't change the data in the +rows between calls. You can change the locations of the data, just +not the data. Each pass only writes the pixels appropriate for that +pass, and assumes the data from previous passes is still valid. + + png_read_rows(png_ptr, row_pointers, NULL, + number_of_rows); + +If you only want the first effect (the rectangles), do the same as +before except pass the row buffer in the third parameter, and leave +the second parameter NULL. + + png_read_rows(png_ptr, NULL, row_pointers, + number_of_rows); + +Finishing a sequential read + +After you are finished reading the image through the +low-level interface, you can finish reading the file. If you are +interested in comments or time, which may be stored either before or +after the image data, you should pass the separate png_info struct if +you want to keep the comments from before and after the image +separate. If you are not interested, you can pass NULL. + + png_read_end(png_ptr, end_info); + +When you are done, you can free all memory allocated by libpng like this: + + png_destroy_read_struct(&png_ptr, &info_ptr, + &end_info); + +It is also possible to individually free the info_ptr members that +point to libpng-allocated storage with the following function: + + png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask + containing the bitwise OR of one or + more of + PNG_FREE_PLTE, PNG_FREE_TRNS, + PNG_FREE_HIST, PNG_FREE_ICCP, + PNG_FREE_PCAL, PNG_FREE_ROWS, + PNG_FREE_SCAL, PNG_FREE_SPLT, + PNG_FREE_TEXT, PNG_FREE_UNKN, + or simply PNG_FREE_ALL + seq - sequence number of item to be freed + (-1 for all items) + +This function may be safely called when the relevant storage has +already been freed, or has not yet been allocated, or was allocated +by the user and not by libpng, and will in those cases do nothing. +The "seq" parameter is ignored if only one item of the selected data +type, such as PLTE, is allowed. If "seq" is not -1, and multiple items +are allowed for the data type identified in the mask, such as text or +sPLT, only the n'th item in the structure is freed, where n is "seq". + +The default behavior is only to free data that was allocated internally +by libpng. This can be changed, so that libpng will not free the data, +or so that it will free data that was allocated by the user with png_malloc() +or png_zalloc() and passed in via a png_set_*() function, with + + png_data_freer(png_ptr, info_ptr, freer, mask) + mask - which data elements are affected + same choices as in png_free_data() + freer - one of + PNG_DESTROY_WILL_FREE_DATA + PNG_SET_WILL_FREE_DATA + PNG_USER_WILL_FREE_DATA + +This function only affects data that has already been allocated. +You can call this function after reading the PNG data but before calling +any png_set_*() functions, to control whether the user or the png_set_*() +function is responsible for freeing any existing data that might be present, +and again after the png_set_*() functions to control whether the user +or png_destroy_*() is supposed to free the data. When the user assumes +responsibility for libpng-allocated data, the application must use +png_free() to free it, and when the user transfers responsibility to libpng +for data that the user has allocated, the user must have used png_malloc() +or png_zalloc() to allocate it. + +If you allocated your row_pointers in a single block, as suggested above in +the description of the high level read interface, you must not transfer +responsibility for freeing it to the png_set_rows or png_read_destroy function, +because they would also try to free the individual row_pointers[i]. + +If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword +separately, do not transfer responsibility for freeing text_ptr to libpng, +because when libpng fills a png_text structure it combines these members with +the key member, and png_free_data() will free only text_ptr.key. Similarly, +if you transfer responsibility for free'ing text_ptr from libpng to your +application, your application must not separately free those members. + +The png_free_data() function will turn off the "valid" flag for anything +it frees. If you need to turn the flag off for a chunk that was freed by +your application instead of by libpng, you can use + + png_set_invalid(png_ptr, info_ptr, mask); + mask - identifies the chunks to be made invalid, + containing the bitwise OR of one or + more of + PNG_INFO_gAMA, PNG_INFO_sBIT, + PNG_INFO_cHRM, PNG_INFO_PLTE, + PNG_INFO_tRNS, PNG_INFO_bKGD, + PNG_INFO_hIST, PNG_INFO_pHYs, + PNG_INFO_oFFs, PNG_INFO_tIME, + PNG_INFO_pCAL, PNG_INFO_sRGB, + PNG_INFO_iCCP, PNG_INFO_sPLT, + PNG_INFO_sCAL, PNG_INFO_IDAT + +For a more compact example of reading a PNG image, see the file example.c. + +Reading PNG files progressively + +The progressive reader is slightly different then the non-progressive +reader. Instead of calling png_read_info(), png_read_rows(), and +png_read_end(), you make one call to png_process_data(), which calls +callbacks when it has the info, a row, or the end of the image. You +set up these callbacks with png_set_progressive_read_fn(). You don't +have to worry about the input/output functions of libpng, as you are +giving the library the data directly in png_process_data(). I will +assume that you have read the section on reading PNG files above, +so I will only highlight the differences (although I will show +all of the code). + +png_structp png_ptr; +png_infop info_ptr; + + /* An example code fragment of how you would + initialize the progressive reader in your + application. */ + int + initialize_png_reader() + { + png_ptr = png_create_read_struct + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + user_error_fn, user_warning_fn); + if (!png_ptr) + return (ERROR); + info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) + { + png_destroy_read_struct(&png_ptr, (png_infopp)NULL, + (png_infopp)NULL); + return (ERROR); + } + + if (setjmp(png_jmpbuf(png_ptr))) + { + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); + } + + /* This one's new. You can provide functions + to be called when the header info is valid, + when each row is completed, and when the image + is finished. If you aren't using all functions, + you can specify NULL parameters. Even when all + three functions are NULL, you need to call + png_set_progressive_read_fn(). You can use + any struct as the user_ptr (cast to a void pointer + for the function call), and retrieve the pointer + from inside the callbacks using the function + + png_get_progressive_ptr(png_ptr); + + which will return a void pointer, which you have + to cast appropriately. + */ + png_set_progressive_read_fn(png_ptr, (void *)user_ptr, + info_callback, row_callback, end_callback); + + return 0; + } + + /* A code fragment that you call as you receive blocks + of data */ + int + process_data(png_bytep buffer, png_uint_32 length) + { + if (setjmp(png_jmpbuf(png_ptr))) + { + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); + } + + /* This one's new also. Simply give it a chunk + of data from the file stream (in order, of + course). On machines with segmented memory + models machines, don't give it any more than + 64K. The library seems to run fine with sizes + of 4K. Although you can give it much less if + necessary (I assume you can give it chunks of + 1 byte, I haven't tried less then 256 bytes + yet). When this function returns, you may + want to display any rows that were generated + in the row callback if you don't already do + so there. + */ + png_process_data(png_ptr, info_ptr, buffer, length); + return 0; + } + + /* This function is called (as set by + png_set_progressive_read_fn() above) when enough data + has been supplied so all of the header has been + read. + */ + void + info_callback(png_structp png_ptr, png_infop info) + { + /* Do any setup here, including setting any of + the transformations mentioned in the Reading + PNG files section. For now, you _must_ call + either png_start_read_image() or + png_read_update_info() after all the + transformations are set (even if you don't set + any). You may start getting rows before + png_process_data() returns, so this is your + last chance to prepare for that. + */ + } + + /* This function is called when each row of image + data is complete */ + void + row_callback(png_structp png_ptr, png_bytep new_row, + png_uint_32 row_num, int pass) + { + /* If the image is interlaced, and you turned + on the interlace handler, this function will + be called for every row in every pass. Some + of these rows will not be changed from the + previous pass. When the row is not changed, + the new_row variable will be NULL. The rows + and passes are called in order, so you don't + really need the row_num and pass, but I'm + supplying them because it may make your life + easier. + + For the non-NULL rows of interlaced images, + you must call png_progressive_combine_row() + passing in the row and the old row. You can + call this function for NULL rows (it will just + return) and for non-interlaced images (it just + does the memcpy for you) if it will make the + code easier. Thus, you can just do this for + all cases: + */ + + png_progressive_combine_row(png_ptr, old_row, + new_row); + + /* where old_row is what was displayed for + previously for the row. Note that the first + pass (pass == 0, really) will completely cover + the old row, so the rows do not have to be + initialized. After the first pass (and only + for interlaced images), you will have to pass + the current row, and the function will combine + the old row and the new row. + */ + } + + void + end_callback(png_structp png_ptr, png_infop info) + { + /* This function is called after the whole image + has been read, including any chunks after the + image (up to and including the IEND). You + will usually have the same info chunk as you + had in the header, although some data may have + been added to the comments and time fields. + + Most people won't do much here, perhaps setting + a flag that marks the image as finished. + */ + } + + + +IV. Writing + +Much of this is very similar to reading. However, everything of +importance is repeated here, so you won't have to constantly look +back up in the reading section to understand writing. + +Setup + +You will want to do the I/O initialization before you get into libpng, +so if it doesn't work, you don't have anything to undo. If you are not +using the standard I/O functions, you will need to replace them with +custom writing functions. See the discussion under Customizing libpng. + + FILE *fp = fopen(file_name, "wb"); + if (!fp) + { + return (ERROR); + } + +Next, png_struct and png_info need to be allocated and initialized. +As these can be both relatively large, you may not want to store these +on the stack, unless you have stack space to spare. Of course, you +will want to check if they return NULL. If you are also reading, +you won't want to name your read structure and your write structure +both "png_ptr"; you can call them anything you like, such as +"read_ptr" and "write_ptr". Look at pngtest.c, for example. + + png_structp png_ptr = png_create_write_struct + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + user_error_fn, user_warning_fn); + if (!png_ptr) + return (ERROR); + + png_infop info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) + { + png_destroy_write_struct(&png_ptr, + (png_infopp)NULL); + return (ERROR); + } + +If you want to use your own memory allocation routines, +define PNG_USER_MEM_SUPPORTED and use +png_create_write_struct_2() instead of png_create_write_struct(): + + png_structp png_ptr = png_create_write_struct_2 + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + user_error_fn, user_warning_fn, (png_voidp) + user_mem_ptr, user_malloc_fn, user_free_fn); + +After you have these structures, you will need to set up the +error handling. When libpng encounters an error, it expects to +longjmp() back to your routine. Therefore, you will need to call +setjmp() and pass the png_jmpbuf(png_ptr). If you +write the file from different routines, you will need to update +the png_jmpbuf(png_ptr) every time you enter a new routine that will +call a png_*() function. See your documentation of setjmp/longjmp +for your compiler for more information on setjmp/longjmp. See +the discussion on libpng error handling in the Customizing Libpng +section below for more information on the libpng error handling. + + if (setjmp(png_jmpbuf(png_ptr))) + { + png_destroy_write_struct(&png_ptr, &info_ptr); + fclose(fp); + return (ERROR); + } + ... + return; + +If you would rather avoid the complexity of setjmp/longjmp issues, +you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +errors will result in a call to PNG_ABORT() which defaults to abort(). + +Now you need to set up the output code. The default for libpng is to +use the C function fwrite(). If you use this, you will need to pass a +valid FILE * in the function png_init_io(). Be sure that the file is +opened in binary mode. Again, if you wish to handle writing data in +another way, see the discussion on libpng I/O handling in the Customizing +Libpng section below. + + png_init_io(png_ptr, fp); + +If you are embedding your PNG into a datastream such as MNG, and don't +want libpng to write the 8-byte signature, or if you have already +written the signature in your application, use + + png_set_sig_bytes(png_ptr, 8); + +to inform libpng that it should not write a signature. + +Write callbacks + +At this point, you can set up a callback function that will be +called after each row has been written, which you can use to control +a progress meter or the like. It's demonstrated in pngtest.c. +You must supply a function + + void write_row_callback(png_ptr, png_uint_32 row, + int pass); + { + /* put your code here */ + } + +(You can give it another name that you like instead of "write_row_callback") + +To inform libpng about your function, use + + png_set_write_status_fn(png_ptr, write_row_callback); + +You now have the option of modifying how the compression library will +run. The following functions are mainly for testing, but may be useful +in some cases, like if you need to write PNG files extremely fast and +are willing to give up some compression, or if you want to get the +maximum possible compression at the expense of slower writing. If you +have no special needs in this area, let the library do what it wants by +not calling this function at all, as it has been tuned to deliver a good +speed/compression ratio. The second parameter to png_set_filter() is +the filter method, for which the only valid values are 0 (as of the +July 1999 PNG specification, version 1.2) or 64 (if you are writing +a PNG datastream that is to be embedded in a MNG datastream). The third +parameter is a flag that indicates which filter type(s) are to be tested +for each scanline. See the PNG specification for details on the specific +filter types. + + + /* turn on or off filtering, and/or choose + specific filters. You can use either a single + PNG_FILTER_VALUE_NAME or the bitwise OR of one + or more PNG_FILTER_NAME masks. */ + png_set_filter(png_ptr, 0, + PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | + PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | + PNG_FILTER_UP | PNG_FILTER_VALUE_UP | + PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG | + PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| + PNG_ALL_FILTERS); + +If an application +wants to start and stop using particular filters during compression, +it should start out with all of the filters (to ensure that the previous +row of pixels will be stored in case it's needed later), and then add +and remove them after the start of compression. + +If you are writing a PNG datastream that is to be embedded in a MNG +datastream, the second parameter can be either 0 or 64. + +The png_set_compression_*() functions interface to the zlib compression +library, and should mostly be ignored unless you really know what you are +doing. The only generally useful call is png_set_compression_level() +which changes how much time zlib spends on trying to compress the image +data. See the Compression Library (zlib.h and algorithm.txt, distributed +with zlib) for details on the compression levels. + + /* set the zlib compression level */ + png_set_compression_level(png_ptr, + Z_BEST_COMPRESSION); + + /* set other zlib parameters */ + png_set_compression_mem_level(png_ptr, 8); + png_set_compression_strategy(png_ptr, + Z_DEFAULT_STRATEGY); + png_set_compression_window_bits(png_ptr, 15); + png_set_compression_method(png_ptr, 8); + png_set_compression_buffer_size(png_ptr, 8192) + +extern PNG_EXPORT(void,png_set_zbuf_size) + +Setting the contents of info for output + +You now need to fill in the png_info structure with all the data you +wish to write before the actual image. Note that the only thing you +are allowed to write after the image is the text chunks and the time +chunk (as of PNG Specification 1.2, anyway). See png_write_end() and +the latest PNG specification for more information on that. If you +wish to write them before the image, fill them in now, and flag that +data as being valid. If you want to wait until after the data, don't +fill them until png_write_end(). For all the fields in png_info and +their data types, see png.h. For explanations of what the fields +contain, see the PNG specification. + +Some of the more important parts of the png_info are: + + png_set_IHDR(png_ptr, info_ptr, width, height, + bit_depth, color_type, interlace_type, + compression_type, filter_method) + width - holds the width of the image + in pixels (up to 2^31). + height - holds the height of the image + in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the + image channels. + (valid values are 1, 2, 4, 8, 16 + and depend also on the + color_type. See also significant + bits (sBIT) below). + color_type - describes which color/alpha + channels are present. + PNG_COLOR_TYPE_GRAY + (bit depths 1, 2, 4, 8, 16) + PNG_COLOR_TYPE_GRAY_ALPHA + (bit depths 8, 16) + PNG_COLOR_TYPE_PALETTE + (bit depths 1, 2, 4, 8) + PNG_COLOR_TYPE_RGB + (bit_depths 8, 16) + PNG_COLOR_TYPE_RGB_ALPHA + (bit_depths 8, 16) + + PNG_COLOR_MASK_PALETTE + PNG_COLOR_MASK_COLOR + PNG_COLOR_MASK_ALPHA + + interlace_type - PNG_INTERLACE_NONE or + PNG_INTERLACE_ADAM7 + compression_type - (must be + PNG_COMPRESSION_TYPE_DEFAULT) + filter_method - (must be PNG_FILTER_TYPE_DEFAULT + or, if you are writing a PNG to + be embedded in a MNG datastream, + can also be + PNG_INTRAPIXEL_DIFFERENCING) + +If you call png_set_IHDR(), the call must appear before any of the +other png_set_*() functions, because they might require access to some of +the IHDR settings. The remaining png_set_*() functions can be called +in any order. + +If you wish, you can reset the compression_type, interlace_type, or +filter_method later by calling png_set_IHDR() again; if you do this, the +width, height, bit_depth, and color_type must be the same in each call. + + png_set_PLTE(png_ptr, info_ptr, palette, + num_palette); + palette - the palette for the file + (array of png_color) + num_palette - number of entries in the palette + + png_set_gAMA(png_ptr, info_ptr, gamma); + gamma - the gamma the image was created + at (PNG_INFO_gAMA) + + png_set_sRGB(png_ptr, info_ptr, srgb_intent); + srgb_intent - the rendering intent + (PNG_INFO_sRGB) The presence of + the sRGB chunk means that the pixel + data is in the sRGB color space. + This chunk also implies specific + values of gAMA and cHRM. Rendering + intent is the CSS-1 property that + has been defined by the International + Color Consortium + (http://www.color.org). + It can be one of + PNG_sRGB_INTENT_SATURATION, + PNG_sRGB_INTENT_PERCEPTUAL, + PNG_sRGB_INTENT_ABSOLUTE, or + PNG_sRGB_INTENT_RELATIVE. + + + png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, + srgb_intent); + srgb_intent - the rendering intent + (PNG_INFO_sRGB) The presence of the + sRGB chunk means that the pixel + data is in the sRGB color space. + This function also causes gAMA and + cHRM chunks with the specific values + that are consistent with sRGB to be + written. + + png_set_iCCP(png_ptr, info_ptr, name, compression_type, + profile, proflen); + name - The profile name. + compression - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + profile - International Color Consortium color + profile data. May contain NULs. + proflen - length of profile data in bytes. + + png_set_sBIT(png_ptr, info_ptr, sig_bit); + sig_bit - the number of significant bits for + (PNG_INFO_sBIT) each of the gray, red, + green, and blue channels, whichever are + appropriate for the given color type + (png_color_16) + + png_set_tRNS(png_ptr, info_ptr, trans, num_trans, + trans_values); + trans - array of transparent + entries for palette (PNG_INFO_tRNS) + trans_values - graylevel or color sample values + (in order red, green, blue) of the + single transparent color for + non-paletted images (PNG_INFO_tRNS) + num_trans - number of transparent entries + (PNG_INFO_tRNS) + + png_set_hIST(png_ptr, info_ptr, hist); + (PNG_INFO_hIST) + hist - histogram of palette (array of + png_uint_16) + + png_set_tIME(png_ptr, info_ptr, mod_time); + mod_time - time image was last modified + (PNG_VALID_tIME) + + png_set_bKGD(png_ptr, info_ptr, background); + background - background color (PNG_VALID_bKGD) + + png_set_text(png_ptr, info_ptr, text_ptr, num_text); + text_ptr - array of png_text holding image + comments + text_ptr[i].compression - type of compression used + on "text" PNG_TEXT_COMPRESSION_NONE + PNG_TEXT_COMPRESSION_zTXt + PNG_ITXT_COMPRESSION_NONE + PNG_ITXT_COMPRESSION_zTXt + text_ptr[i].key - keyword for comment. Must contain + 1-79 characters. + text_ptr[i].text - text comments for current + keyword. Can be NULL or empty. + text_ptr[i].text_length - length of text string, + after decompression, 0 for iTXt + text_ptr[i].itxt_length - length of itxt string, + after decompression, 0 for tEXt/zTXt + text_ptr[i].lang - language of comment (NULL or + empty for unknown). + text_ptr[i].translated_keyword - keyword in UTF-8 (NULL + or empty for unknown). + Note that the itxt_length, lang, and lang_key + members of the text_ptr structure only exist + when the library is built with iTXt chunk support. + + num_text - number of comments + + png_set_sPLT(png_ptr, info_ptr, &palette_ptr, + num_spalettes); + palette_ptr - array of png_sPLT_struct structures + to be added to the list of palettes + in the info structure. + num_spalettes - number of palette structures to be + added. + + png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, + unit_type); + offset_x - positive offset from the left + edge of the screen + offset_y - positive offset from the top + edge of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER + + png_set_pHYs(png_ptr, info_ptr, res_x, res_y, + unit_type); + res_x - pixels/unit physical resolution + in x direction + res_y - pixels/unit physical resolution + in y direction + unit_type - PNG_RESOLUTION_UNKNOWN, + PNG_RESOLUTION_METER + + png_set_sCAL(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units + (width and height are doubles) + + png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units + (width and height are strings like "2.54") + + png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, + num_unknowns) + unknowns - array of png_unknown_chunk + structures holding unknown chunks + unknowns[i].name - name of unknown chunk + unknowns[i].data - data of unknown chunk + unknowns[i].size - size of unknown chunk's data + unknowns[i].location - position to write chunk in file + 0: do not write chunk + PNG_HAVE_IHDR: before PLTE + PNG_HAVE_PLTE: before IDAT + PNG_AFTER_IDAT: after IDAT + +The "location" member is set automatically according to +what part of the output file has already been written. +You can change its value after calling png_set_unknown_chunks() +as demonstrated in pngtest.c. Within each of the "locations", +the chunks are sequenced according to their position in the +structure (that is, the value of "i", which is the order in which +the chunk was either read from the input file or defined with +png_set_unknown_chunks). + +A quick word about text and num_text. text is an array of png_text +structures. num_text is the number of valid structures in the array. +Each png_text structure holds a language code, a keyword, a text value, +and a compression type. + +The compression types have the same valid numbers as the compression +types of the image data. Currently, the only valid number is zero. +However, you can store text either compressed or uncompressed, unlike +images, which always have to be compressed. So if you don't want the +text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE. +Because tEXt and zTXt chunks don't have a language field, if you +specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt +any language code or translated keyword will not be written out. + +Until text gets around 1000 bytes, it is not worth compressing it. +After the text has been written out to the file, the compression type +is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, +so that it isn't written out again at the end (in case you are calling +png_write_end() with the same struct. + +The keywords that are given in the PNG Specification are: + + Title Short (one line) title or + caption for image + Author Name of image's creator + Description Description of image (possibly long) + Copyright Copyright notice + Creation Time Time of original image creation + (usually RFC 1123 format, see below) + Software Software used to create the image + Disclaimer Legal disclaimer + Warning Warning of nature of content + Source Device used to create the image + Comment Miscellaneous comment; conversion + from other image format + +The keyword-text pairs work like this. Keywords should be short +simple descriptions of what the comment is about. Some typical +keywords are found in the PNG specification, as is some recommendations +on keywords. You can repeat keywords in a file. You can even write +some text before the image and some after. For example, you may want +to put a description of the image before the image, but leave the +disclaimer until after, so viewers working over modem connections +don't have to wait for the disclaimer to go over the modem before +they start seeing the image. Finally, keywords should be full +words, not abbreviations. Keywords and text are in the ISO 8859-1 +(Latin-1) character set (a superset of regular ASCII) and can not +contain NUL characters, and should not contain control or other +unprintable characters. To make the comments widely readable, stick +with basic ASCII, and avoid machine specific character set extensions +like the IBM-PC character set. The keyword must be present, but +you can leave off the text string on non-compressed pairs. +Compressed pairs must have a text string, as only the text string +is compressed anyway, so the compression would be meaningless. + +PNG supports modification time via the png_time structure. Two +conversion routines are provided, png_convert_from_time_t() for +time_t and png_convert_from_struct_tm() for struct tm. The +time_t routine uses gmtime(). You don't have to use either of +these, but if you wish to fill in the png_time structure directly, +you should provide the time in universal time (GMT) if possible +instead of your local time. Note that the year number is the full +year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and +that months start with 1. + +If you want to store the time of the original image creation, you should +use a plain tEXt chunk with the "Creation Time" keyword. This is +necessary because the "creation time" of a PNG image is somewhat vague, +depending on whether you mean the PNG file, the time the image was +created in a non-PNG format, a still photo from which the image was +scanned, or possibly the subject matter itself. In order to facilitate +machine-readable dates, it is recommended that the "Creation Time" +tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"), +although this isn't a requirement. Unlike the tIME chunk, the +"Creation Time" tEXt chunk is not expected to be automatically changed +by the software. To facilitate the use of RFC 1123 dates, a function +png_convert_to_rfc1123(png_timep) is provided to convert from PNG +time to an RFC 1123 format string. + +Writing unknown chunks + +You can use the png_set_unknown_chunks function to queue up chunks +for writing. You give it a chunk name, raw data, and a size; that's +all there is to it. The chunks will be written by the next following +png_write_info_before_PLTE, png_write_info, or png_write_end function. +Any chunks previously read into the info structure's unknown-chunk +list will also be written out in a sequence that satisfies the PNG +specification's ordering rules. + +The high-level write interface + +At this point there are two ways to proceed; through the high-level +write interface, or through a sequence of low-level write operations. +You can use the high-level interface if your image data is present +in the info structure. All defined output +transformations are permitted, enabled by the following masks. + + PNG_TRANSFORM_IDENTITY No transformation + PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples + PNG_TRANSFORM_PACKSWAP Change order of packed + pixels to LSB first + PNG_TRANSFORM_INVERT_MONO Invert monochrome images + PNG_TRANSFORM_SHIFT Normalize pixels to the + sBIT depth + PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA + to BGRA + PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA + to AG + PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity + to transparency + PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples + PNG_TRANSFORM_STRIP_FILLER Strip out filler + bytes (deprecated). + PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading + filler bytes + PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing + filler bytes + +If you have valid image data in the info structure (you can use +png_set_rows() to put image data in the info structure), simply do this: + + png_write_png(png_ptr, info_ptr, png_transforms, NULL) + +where png_transforms is an integer containing the bitwise OR of some set of +transformation flags. This call is equivalent to png_write_info(), +followed the set of transformations indicated by the transform mask, +then png_write_image(), and finally png_write_end(). + +(The final parameter of this call is not yet used. Someday it might point +to transformation parameters required by some future output transform.) + +You must use png_transforms and not call any png_set_transform() functions +when you use png_write_png(). + +The low-level write interface + +If you are going the low-level route instead, you are now ready to +write all the file information up to the actual image data. You do +this with a call to png_write_info(). + + png_write_info(png_ptr, info_ptr); + +Note that there is one transformation you may need to do before +png_write_info(). In PNG files, the alpha channel in an image is the +level of opacity. If your data is supplied as a level of transparency, +you can invert the alpha channel before you write it, so that 0 is +fully transparent and 255 (in 8-bit or paletted images) or 65535 +(in 16-bit images) is fully opaque, with + + png_set_invert_alpha(png_ptr); + +This must appear before png_write_info() instead of later with the +other transformations because in the case of paletted images the tRNS +chunk data has to be inverted before the tRNS chunk is written. If +your image is not a paletted image, the tRNS data (which in such cases +represents a single color to be rendered as transparent) won't need to +be changed, and you can safely do this transformation after your +png_write_info() call. + +If you need to write a private chunk that you want to appear before +the PLTE chunk when PLTE is present, you can write the PNG info in +two steps, and insert code to write your own chunk between them: + + png_write_info_before_PLTE(png_ptr, info_ptr); + png_set_unknown_chunks(png_ptr, info_ptr, ...); + png_write_info(png_ptr, info_ptr); + +After you've written the file information, you can set up the library +to handle any special transformations of the image data. The various +ways to transform the data will be described in the order that they +should occur. This is important, as some of these change the color +type and/or bit depth of the data, and some others only work on +certain color types and bit depths. Even though each transformation +checks to see if it has data that it can do something with, you should +make sure to only enable a transformation if it will be valid for the +data. For example, don't swap red and blue on grayscale data. + +PNG files store RGB pixels packed into 3 or 6 bytes. This code tells +the library to strip input data that has 4 or 8 bytes per pixel down +to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2 +bytes per pixel). + + png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); + +where the 0 is unused, and the location is either PNG_FILLER_BEFORE or +PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel +is stored XRGB or RGBX. + +PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as +they can, resulting in, for example, 8 pixels per byte for 1 bit files. +If the data is supplied at 1 pixel per byte, use this code, which will +correctly pack the pixels into a single byte: + + png_set_packing(png_ptr); + +PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your +data is of another bit depth, you can write an sBIT chunk into the +file so that decoders can recover the original data if desired. + + /* Set the true bit depth of the image data */ + if (color_type & PNG_COLOR_MASK_COLOR) + { + sig_bit.red = true_bit_depth; + sig_bit.green = true_bit_depth; + sig_bit.blue = true_bit_depth; + } + else + { + sig_bit.gray = true_bit_depth; + } + if (color_type & PNG_COLOR_MASK_ALPHA) + { + sig_bit.alpha = true_bit_depth; + } + + png_set_sBIT(png_ptr, info_ptr, &sig_bit); + +If the data is stored in the row buffer in a bit depth other than +one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG), +this will scale the values to appear to be the correct bit depth as +is required by PNG. + + png_set_shift(png_ptr, &sig_bit); + +PNG files store 16 bit pixels in network byte order (big-endian, +ie. most significant bits first). This code would be used if they are +supplied the other way (little-endian, i.e. least significant bits +first, the way PCs store them): + + if (bit_depth > 8) + png_set_swap(png_ptr); + +If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you +need to change the order the pixels are packed into bytes, you can use: + + if (bit_depth < 8) + png_set_packswap(png_ptr); + +PNG files store 3 color pixels in red, green, blue order. This code +would be used if they are supplied as blue, green, red: + + png_set_bgr(png_ptr); + +PNG files describe monochrome as black being zero and white being +one. This code would be used if the pixels are supplied with this reversed +(black being one and white being zero): + + png_set_invert_mono(png_ptr); + +Finally, you can write your own transformation function if none of +the existing ones meets your needs. This is done by setting a callback +with + + png_set_write_user_transform_fn(png_ptr, + write_transform_fn); + +You must supply the function + + void write_transform_fn(png_ptr ptr, row_info_ptr + row_info, png_bytep data) + +See pngtest.c for a working example. Your function will be called +before any of the other transformations are processed. + +You can also set up a pointer to a user structure for use by your +callback function. + + png_set_user_transform_info(png_ptr, user_ptr, 0, 0); + +The user_channels and user_depth parameters of this function are ignored +when writing; you can set them to zero as shown. + +You can retrieve the pointer via the function png_get_user_transform_ptr(). +For example: + + voidp write_user_transform_ptr = + png_get_user_transform_ptr(png_ptr); + +It is possible to have libpng flush any pending output, either manually, +or automatically after a certain number of lines have been written. To +flush the output stream a single time call: + + png_write_flush(png_ptr); + +and to have libpng flush the output stream periodically after a certain +number of scanlines have been written, call: + + png_set_flush(png_ptr, nrows); + +Note that the distance between rows is from the last time png_write_flush() +was called, or the first row of the image if it has never been called. +So if you write 50 lines, and then png_set_flush 25, it will flush the +output on the next scanline, and every 25 lines thereafter, unless +png_write_flush() is called before 25 more lines have been written. +If nrows is too small (less than about 10 lines for a 640 pixel wide +RGB image) the image compression may decrease noticeably (although this +may be acceptable for real-time applications). Infrequent flushing will +only degrade the compression performance by a few percent over images +that do not use flushing. + +Writing the image data + +That's it for the transformations. Now you can write the image data. +The simplest way to do this is in one function call. If you have the +whole image in memory, you can just call png_write_image() and libpng +will write the image. You will need to pass in an array of pointers to +each row. This function automatically handles interlacing, so you don't +need to call png_set_interlace_handling() or call this function multiple +times, or any of that other stuff necessary with png_write_rows(). + + png_write_image(png_ptr, row_pointers); + +where row_pointers is: + + png_byte *row_pointers[height]; + +You can point to void or char or whatever you use for pixels. + +If you don't want to write the whole image at once, you can +use png_write_rows() instead. If the file is not interlaced, +this is simple: + + png_write_rows(png_ptr, row_pointers, + number_of_rows); + +row_pointers is the same as in the png_write_image() call. + +If you are just writing one row at a time, you can do this with +a single row_pointer instead of an array of row_pointers: + + png_bytep row_pointer = row; + + png_write_row(png_ptr, row_pointer); + +When the file is interlaced, things can get a good deal more complicated. +The only currently (as of the PNG Specification version 1.2, dated July +1999) defined interlacing scheme for PNG files is the "Adam7" interlace +scheme, that breaks down an image into seven smaller images of varying +size. libpng will build these images for you, or you can do them +yourself. If you want to build them yourself, see the PNG specification +for details of which pixels to write when. + +If you don't want libpng to handle the interlacing details, just +use png_set_interlace_handling() and call png_write_rows() the +correct number of times to write all seven sub-images. + +If you want libpng to build the sub-images, call this before you start +writing any rows: + + number_of_passes = + png_set_interlace_handling(png_ptr); + +This will return the number of passes needed. Currently, this is seven, +but may change if another interlace type is added. + +Then write the complete image number_of_passes times. + + png_write_rows(png_ptr, row_pointers, + number_of_rows); + +As some of these rows are not used, and thus return immediately, you may +want to read about interlacing in the PNG specification, and only update +the rows that are actually used. + +Finishing a sequential write + +After you are finished writing the image, you should finish writing +the file. If you are interested in writing comments or time, you should +pass an appropriately filled png_info pointer. If you are not interested, +you can pass NULL. + + png_write_end(png_ptr, info_ptr); + +When you are done, you can free all memory used by libpng like this: + + png_destroy_write_struct(&png_ptr, &info_ptr); + +It is also possible to individually free the info_ptr members that +point to libpng-allocated storage with the following function: + + png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask + containing the bitwise OR of one or + more of + PNG_FREE_PLTE, PNG_FREE_TRNS, + PNG_FREE_HIST, PNG_FREE_ICCP, + PNG_FREE_PCAL, PNG_FREE_ROWS, + PNG_FREE_SCAL, PNG_FREE_SPLT, + PNG_FREE_TEXT, PNG_FREE_UNKN, + or simply PNG_FREE_ALL + seq - sequence number of item to be freed + (-1 for all items) + +This function may be safely called when the relevant storage has +already been freed, or has not yet been allocated, or was allocated +by the user and not by libpng, and will in those cases do nothing. +The "seq" parameter is ignored if only one item of the selected data +type, such as PLTE, is allowed. If "seq" is not -1, and multiple items +are allowed for the data type identified in the mask, such as text or +sPLT, only the n'th item in the structure is freed, where n is "seq". + +If you allocated data such as a palette that you passed in to libpng +with png_set_*, you must not free it until just before the call to +png_destroy_write_struct(). + +The default behavior is only to free data that was allocated internally +by libpng. This can be changed, so that libpng will not free the data, +or so that it will free data that was allocated by the user with png_malloc() +or png_zalloc() and passed in via a png_set_*() function, with + + png_data_freer(png_ptr, info_ptr, freer, mask) + mask - which data elements are affected + same choices as in png_free_data() + freer - one of + PNG_DESTROY_WILL_FREE_DATA + PNG_SET_WILL_FREE_DATA + PNG_USER_WILL_FREE_DATA + +For example, to transfer responsibility for some data from a read structure +to a write structure, you could use + + png_data_freer(read_ptr, read_info_ptr, + PNG_USER_WILL_FREE_DATA, + PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) + png_data_freer(write_ptr, write_info_ptr, + PNG_DESTROY_WILL_FREE_DATA, + PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) + +thereby briefly reassigning responsibility for freeing to the user but +immediately afterwards reassigning it once more to the write_destroy +function. Having done this, it would then be safe to destroy the read +structure and continue to use the PLTE, tRNS, and hIST data in the write +structure. + +This function only affects data that has already been allocated. +You can call this function before calling after the png_set_*() functions +to control whether the user or png_destroy_*() is supposed to free the data. +When the user assumes responsibility for libpng-allocated data, the +application must use +png_free() to free it, and when the user transfers responsibility to libpng +for data that the user has allocated, the user must have used png_malloc() +or png_zalloc() to allocate it. + +If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword +separately, do not transfer responsibility for freeing text_ptr to libpng, +because when libpng fills a png_text structure it combines these members with +the key member, and png_free_data() will free only text_ptr.key. Similarly, +if you transfer responsibility for free'ing text_ptr from libpng to your +application, your application must not separately free those members. +For a more compact example of writing a PNG image, see the file example.c. + +V. Modifying/Customizing libpng: + +There are two issues here. The first is changing how libpng does +standard things like memory allocation, input/output, and error handling. +The second deals with more complicated things like adding new chunks, +adding new transformations, and generally changing how libpng works. +Both of those are compile-time issues; that is, they are generally +determined at the time the code is written, and there is rarely a need +to provide the user with a means of changing them. + +Memory allocation, input/output, and error handling + +All of the memory allocation, input/output, and error handling in libpng +goes through callbacks that are user-settable. The default routines are +in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change +these functions, call the appropriate png_set_*_fn() function. + +Memory allocation is done through the functions png_malloc(), png_calloc(), +and png_free(). These currently just call the standard C functions. +png_calloc() calls png_malloc() and then png_memset() to clear the newly +allocated memory to zero. If your pointers can't access more then 64K +at a time, you will want to set MAXSEG_64K in zlib.h. Since it is +unlikely that the method of handling memory allocation on a platform +will change between applications, these functions must be modified in +the library at compile time. If you prefer to use a different method +of allocating and freeing data, you can use png_create_read_struct_2() or +png_create_write_struct_2() to register your own functions as described +above. These functions also provide a void pointer that can be retrieved +via + + mem_ptr=png_get_mem_ptr(png_ptr); + +Your replacement memory functions must have prototypes as follows: + + png_voidp malloc_fn(png_structp png_ptr, + png_size_t size); + void free_fn(png_structp png_ptr, png_voidp ptr); + +Your malloc_fn() must return NULL in case of failure. The png_malloc() +function will normally call png_error() if it receives a NULL from the +system memory allocator or from your replacement malloc_fn(). + +Your free_fn() will never be called with a NULL ptr, since libpng's +png_free() checks for NULL before calling free_fn(). + +Input/Output in libpng is done through png_read() and png_write(), +which currently just call fread() and fwrite(). The FILE * is stored in +png_struct and is initialized via png_init_io(). If you wish to change +the method of I/O, the library supplies callbacks that you can set +through the function png_set_read_fn() and png_set_write_fn() at run +time, instead of calling the png_init_io() function. These functions +also provide a void pointer that can be retrieved via the function +png_get_io_ptr(). For example: + + png_set_read_fn(png_structp read_ptr, + voidp read_io_ptr, png_rw_ptr read_data_fn) + + png_set_write_fn(png_structp write_ptr, + voidp write_io_ptr, png_rw_ptr write_data_fn, + png_flush_ptr output_flush_fn); + + voidp read_io_ptr = png_get_io_ptr(read_ptr); + voidp write_io_ptr = png_get_io_ptr(write_ptr); + +The replacement I/O functions must have prototypes as follows: + + void user_read_data(png_structp png_ptr, + png_bytep data, png_size_t length); + void user_write_data(png_structp png_ptr, + png_bytep data, png_size_t length); + void user_flush_data(png_structp png_ptr); + +The user_read_data() function is responsible for detecting and +handling end-of-data errors. + +Supplying NULL for the read, write, or flush functions sets them back +to using the default C stream functions, which expect the io_ptr to +point to a standard *FILE structure. It is probably a mistake +to use NULL for one of write_data_fn and output_flush_fn but not both +of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined. +It is an error to read from a write stream, and vice versa. + +Error handling in libpng is done through png_error() and png_warning(). +Errors handled through png_error() are fatal, meaning that png_error() +should never return to its caller. Currently, this is handled via +setjmp() and longjmp() (unless you have compiled libpng with +PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()), +but you could change this to do things like exit() if you should wish. + +On non-fatal errors, png_warning() is called +to print a warning message, and then control returns to the calling code. +By default png_error() and png_warning() print a message on stderr via +fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined +(because you don't want the messages) or PNG_NO_STDIO defined (because +fprintf() isn't available). If you wish to change the behavior of the error +functions, you will need to set up your own message callbacks. These +functions are normally supplied at the time that the png_struct is created. +It is also possible to redirect errors and warnings to your own replacement +functions after png_create_*_struct() has been called by calling: + + png_set_error_fn(png_structp png_ptr, + png_voidp error_ptr, png_error_ptr error_fn, + png_error_ptr warning_fn); + + png_voidp error_ptr = png_get_error_ptr(png_ptr); + +If NULL is supplied for either error_fn or warning_fn, then the libpng +default function will be used, calling fprintf() and/or longjmp() if a +problem is encountered. The replacement error functions should have +parameters as follows: + + void user_error_fn(png_structp png_ptr, + png_const_charp error_msg); + void user_warning_fn(png_structp png_ptr, + png_const_charp warning_msg); + +The motivation behind using setjmp() and longjmp() is the C++ throw and +catch exception handling methods. This makes the code much easier to write, +as there is no need to check every return code of every function call. +However, there are some uncertainties about the status of local variables +after a longjmp, so the user may want to be careful about doing anything +after setjmp returns non-zero besides returning itself. Consult your +compiler documentation for more details. For an alternative approach, you +may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net). + +Custom chunks + +If you need to read or write custom chunks, you may need to get deeper +into the libpng code. The library now has mechanisms for storing +and writing chunks of unknown type; you can even declare callbacks +for custom chunks. However, this may not be good enough if the +library code itself needs to know about interactions between your +chunk and existing `intrinsic' chunks. + +If you need to write a new intrinsic chunk, first read the PNG +specification. Acquire a first level of understanding of how it works. +Pay particular attention to the sections that describe chunk names, +and look at how other chunks were designed, so you can do things +similarly. Second, check out the sections of libpng that read and +write chunks. Try to find a chunk that is similar to yours and use +it as a template. More details can be found in the comments inside +the code. It is best to handle unknown chunks in a generic method, +via callback functions, instead of by modifying libpng functions. + +If you wish to write your own transformation for the data, look through +the part of the code that does the transformations, and check out some of +the simpler ones to get an idea of how they work. Try to find a similar +transformation to the one you want to add and copy off of it. More details +can be found in the comments inside the code itself. + +Configuring for 16 bit platforms + +You will want to look into zconf.h to tell zlib (and thus libpng) that +it cannot allocate more then 64K at a time. Even if you can, the memory +won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K. + +Configuring for DOS + +For DOS users who only have access to the lower 640K, you will +have to limit zlib's memory usage via a png_set_compression_mem_level() +call. See zlib.h or zconf.h in the zlib library for more information. + +Configuring for Medium Model + +Libpng's support for medium model has been tested on most of the popular +compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets +defined, and FAR gets defined to far in pngconf.h, and you should be +all set. Everything in the library (except for zlib's structure) is +expecting far data. You must use the typedefs with the p or pp on +the end for pointers (or at least look at them and be careful). Make +note that the rows of data are defined as png_bytepp, which is an +unsigned char far * far *. + +Configuring for gui/windowing platforms: + +You will need to write new error and warning functions that use the GUI +interface, as described previously, and set them to be the error and +warning functions at the time that png_create_*_struct() is called, +in order to have them available during the structure initialization. +They can be changed later via png_set_error_fn(). On some compilers, +you may also have to change the memory allocators (png_malloc, etc.). + +Configuring for compiler xxx: + +All includes for libpng are in pngconf.h. If you need to add, change +or delete an include, this is the place to do it. +The includes that are not needed outside libpng are protected by the +PNG_INTERNAL definition, which is only defined for those routines inside +libpng itself. The files in libpng proper only include png.h, which +includes pngconf.h. + +Configuring zlib: + +There are special functions to configure the compression. Perhaps the +most useful one changes the compression level, which currently uses +input compression values in the range 0 - 9. The library normally +uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests +have shown that for a large majority of images, compression values in +the range 3-6 compress nearly as well as higher levels, and do so much +faster. For online applications it may be desirable to have maximum speed +(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also +specify no compression (Z_NO_COMPRESSION = 0), but this would create +files larger than just storing the raw bitmap. You can specify the +compression level by calling: + + png_set_compression_level(png_ptr, level); + +Another useful one is to reduce the memory level used by the library. +The memory level defaults to 8, but it can be lowered if you are +short on memory (running DOS, for example, where you only have 640K). +Note that the memory level does have an effect on compression; among +other things, lower levels will result in sections of incompressible +data being emitted in smaller stored blocks, with a correspondingly +larger relative overhead of up to 15% in the worst case. + + png_set_compression_mem_level(png_ptr, level); + +The other functions are for configuring zlib. They are not recommended +for normal use and may result in writing an invalid PNG file. See +zlib.h for more information on what these mean. + + png_set_compression_strategy(png_ptr, + strategy); + png_set_compression_window_bits(png_ptr, + window_bits); + png_set_compression_method(png_ptr, method); + png_set_compression_buffer_size(png_ptr, size); + +Controlling row filtering + +If you want to control whether libpng uses filtering or not, which +filters are used, and how it goes about picking row filters, you +can call one of these functions. The selection and configuration +of row filters can have a significant impact on the size and +encoding speed and a somewhat lesser impact on the decoding speed +of an image. Filtering is enabled by default for RGB and grayscale +images (with and without alpha), but not for paletted images nor +for any images with bit depths less than 8 bits/pixel. + +The 'method' parameter sets the main filtering method, which is +currently only '0' in the PNG 1.2 specification. The 'filters' +parameter sets which filter(s), if any, should be used for each +scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS +to turn filtering on and off, respectively. + +Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB, +PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise +ORed together with '|' to specify one or more filters to use. +These filters are described in more detail in the PNG specification. +If you intend to change the filter type during the course of writing +the image, you should start with flags set for all of the filters +you intend to use so that libpng can initialize its internal +structures appropriately for all of the filter types. (Note that this +means the first row must always be adaptively filtered, because libpng +currently does not allocate the filter buffers until png_write_row() +is called for the first time.) + + filters = PNG_FILTER_NONE | PNG_FILTER_SUB + PNG_FILTER_UP | PNG_FILTER_AVG | + PNG_FILTER_PAETH | PNG_ALL_FILTERS; + + png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, + filters); + The second parameter can also be + PNG_INTRAPIXEL_DIFFERENCING if you are + writing a PNG to be embedded in a MNG + datastream. This parameter must be the + same as the value of filter_method used + in png_set_IHDR(). + +It is also possible to influence how libpng chooses from among the +available filters. This is done in one or both of two ways - by +telling it how important it is to keep the same filter for successive +rows, and by telling it the relative computational costs of the filters. + + double weights[3] = {1.5, 1.3, 1.1}, + costs[PNG_FILTER_VALUE_LAST] = + {1.0, 1.3, 1.3, 1.5, 1.7}; + + png_set_filter_heuristics(png_ptr, + PNG_FILTER_HEURISTIC_WEIGHTED, 3, + weights, costs); + +The weights are multiplying factors that indicate to libpng that the +row filter should be the same for successive rows unless another row filter +is that many times better than the previous filter. In the above example, +if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a +"sum of absolute differences" 1.5 x 1.3 times higher than other filters +and still be chosen, while the NONE filter could have a sum 1.1 times +higher than other filters and still be chosen. Unspecified weights are +taken to be 1.0, and the specified weights should probably be declining +like those above in order to emphasize recent filters over older filters. + +The filter costs specify for each filter type a relative decoding cost +to be considered when selecting row filters. This means that filters +with higher costs are less likely to be chosen over filters with lower +costs, unless their "sum of absolute differences" is that much smaller. +The costs do not necessarily reflect the exact computational speeds of +the various filters, since this would unduly influence the final image +size. + +Note that the numbers above were invented purely for this example and +are given only to help explain the function usage. Little testing has +been done to find optimum values for either the costs or the weights. + +Removing unwanted object code + +There are a bunch of #define's in pngconf.h that control what parts of +libpng are compiled. All the defines end in _SUPPORTED. If you are +never going to use a capability, you can change the #define to #undef +before recompiling libpng and save yourself code and data space, or +you can turn off individual capabilities with defines that begin with +PNG_NO_. + +You can also turn all of the transforms and ancillary chunk capabilities +off en masse with compiler directives that define +PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, +or all four, +along with directives to turn on any of the capabilities that you do +want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra +transformations but still leave the library fully capable of reading +and writing PNG files with all known public chunks. Use of the +PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library +that is incapable of reading or writing ancillary chunks. If you are +not using the progressive reading capability, you can turn that off +with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING +capability, which you'll still have). + +All the reading and writing specific code are in separate files, so the +linker should only grab the files it needs. However, if you want to +make sure, or if you are building a stand alone library, all the +reading files start with pngr and all the writing files start with +pngw. The files that don't match either (like png.c, pngtrans.c, etc.) +are used for both reading and writing, and always need to be included. +The progressive reader is in pngpread.c + +If you are creating or distributing a dynamically linked library (a .so +or DLL file), you should not remove or disable any parts of the library, +as this will cause applications linked with different versions of the +library to fail if they call functions not available in your library. +The size of the library itself should not be an issue, because only +those sections that are actually used will be loaded into memory. + +Requesting debug printout + +The macro definition PNG_DEBUG can be used to request debugging +printout. Set it to an integer value in the range 0 to 3. Higher +numbers result in increasing amounts of debugging information. The +information is printed to the "stderr" file, unless another file +name is specified in the PNG_DEBUG_FILE macro definition. + +When PNG_DEBUG > 0, the following functions (macros) become available: + + png_debug(level, message) + png_debug1(level, message, p1) + png_debug2(level, message, p1, p2) + +in which "level" is compared to PNG_DEBUG to decide whether to print +the message, "message" is the formatted string to be printed, +and p1 and p2 are parameters that are to be embedded in the string +according to printf-style formatting directives. For example, + + png_debug1(2, "foo=%d\n", foo); + +is expanded to + + if(PNG_DEBUG > 2) + fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); + +When PNG_DEBUG is defined but is zero, the macros aren't defined, but you +can still use PNG_DEBUG to control your own debugging: + + #ifdef PNG_DEBUG + fprintf(stderr, ... + #endif + +When PNG_DEBUG = 1, the macros are defined, but only png_debug statements +having level = 0 will be printed. There aren't any such statements in +this version of libpng, but if you insert some they will be printed. + +VI. MNG support + +The MNG specification (available at http://www.libpng.org/pub/mng) allows +certain extensions to PNG for PNG images that are embedded in MNG datastreams. +Libpng can support some of these extensions. To enable them, use the +png_permit_mng_features() function: + + feature_set = png_permit_mng_features(png_ptr, mask) + mask is a png_uint_32 containing the bitwise OR of the + features you want to enable. These include + PNG_FLAG_MNG_EMPTY_PLTE + PNG_FLAG_MNG_FILTER_64 + PNG_ALL_MNG_FEATURES + feature_set is a png_uint_32 that is the bitwise AND of + your mask with the set of MNG features that is + supported by the version of libpng that you are using. + +It is an error to use this function when reading or writing a standalone +PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped +in a MNG datastream. As a minimum, it must have the MNG 8-byte signature +and the MHDR and MEND chunks. Libpng does not provide support for these +or any other MNG chunks; your application must provide its own support for +them. You may wish to consider using libmng (available at +http://www.libmng.com) instead. + +VII. Changes to Libpng from version 0.88 + +It should be noted that versions of libpng later than 0.96 are not +distributed by the original libpng author, Guy Schalnat, nor by +Andreas Dilger, who had taken over from Guy during 1996 and 1997, and +distributed versions 0.89 through 0.96, but rather by another member +of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are +still alive and well, but they have moved on to other things. + +The old libpng functions png_read_init(), png_write_init(), +png_info_init(), png_read_destroy(), and png_write_destroy() have been +moved to PNG_INTERNAL in version 0.95 to discourage their use. These +functions will be removed from libpng version 2.0.0. + +The preferred method of creating and initializing the libpng structures is +via the png_create_read_struct(), png_create_write_struct(), and +png_create_info_struct() because they isolate the size of the structures +from the application, allow version error checking, and also allow the +use of custom error handling routines during the initialization, which +the old functions do not. The functions png_read_destroy() and +png_write_destroy() do not actually free the memory that libpng +allocated for these structs, but just reset the data structures, so they +can be used instead of png_destroy_read_struct() and +png_destroy_write_struct() if you feel there is too much system overhead +allocating and freeing the png_struct for each image read. + +Setting the error callbacks via png_set_message_fn() before +png_read_init() as was suggested in libpng-0.88 is no longer supported +because this caused applications that do not use custom error functions +to fail if the png_ptr was not initialized to zero. It is still possible +to set the error callbacks AFTER png_read_init(), or to change them with +png_set_error_fn(), which is essentially the same function, but with a new +name to force compilation errors with applications that try to use the old +method. + +Starting with version 1.0.7, you can find out which version of the library +you are using at run-time: + + png_uint_32 libpng_vn = png_access_version_number(); + +The number libpng_vn is constructed from the major version, minor +version with leading zero, and release number with leading zero, +(e.g., libpng_vn for version 1.0.7 is 10007). + +You can also check which version of png.h you used when compiling your +application: + + png_uint_32 application_vn = PNG_LIBPNG_VER; + +VIII. Changes to Libpng from version 1.0.x to 1.2.x + +Support for user memory management was enabled by default. To +accomplish this, the functions png_create_read_struct_2(), +png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(), +png_malloc_default(), and png_free_default() were added. + +Support for the iTXt chunk has been enabled by default as of +version 1.2.41. + +Support for certain MNG features was enabled. + +Support for numbered error messages was added. However, we never got +around to actually numbering the error messages. The function +png_set_strip_error_numbers() was added (Note: the prototype for this +function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE +builds of libpng-1.2.15. It was restored in libpng-1.2.36). + +The png_malloc_warn() function was added at libpng-1.2.3. This issues +a png_warning and returns NULL instead of aborting when it fails to +acquire the requested memory allocation. + +Support for setting user limits on image width and height was enabled +by default. The functions png_set_user_limits(), png_get_user_width_max(), +and png_get_user_height_max() were added at libpng-1.2.6. + +The png_set_add_alpha() function was added at libpng-1.2.7. + +The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9. +Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the +tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is +deprecated. + +A number of macro definitions in support of runtime selection of +assembler code features (especially Intel MMX code support) were +added at libpng-1.2.0: + + PNG_ASM_FLAG_MMX_SUPPORT_COMPILED + PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU + PNG_ASM_FLAG_MMX_READ_COMBINE_ROW + PNG_ASM_FLAG_MMX_READ_INTERLACE + PNG_ASM_FLAG_MMX_READ_FILTER_SUB + PNG_ASM_FLAG_MMX_READ_FILTER_UP + PNG_ASM_FLAG_MMX_READ_FILTER_AVG + PNG_ASM_FLAG_MMX_READ_FILTER_PAETH + PNG_ASM_FLAGS_INITIALIZED + PNG_MMX_READ_FLAGS + PNG_MMX_FLAGS + PNG_MMX_WRITE_FLAGS + PNG_MMX_FLAGS + +We added the following functions in support of runtime +selection of assembler code features: + + png_get_mmx_flagmask() + png_set_mmx_thresholds() + png_get_asm_flags() + png_get_mmx_bitdepth_threshold() + png_get_mmx_rowbytes_threshold() + png_set_asm_flags() + +We replaced all of these functions with simple stubs in libpng-1.2.20, +when the Intel assembler code was removed due to a licensing issue. + +These macros are deprecated: + + PNG_READ_TRANSFORMS_NOT_SUPPORTED + PNG_PROGRESSIVE_READ_NOT_SUPPORTED + PNG_NO_SEQUENTIAL_READ_SUPPORTED + PNG_WRITE_TRANSFORMS_NOT_SUPPORTED + PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED + PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED + +They have been replaced, respectively, by: + + PNG_NO_READ_TRANSFORMS + PNG_NO_PROGRESSIVE_READ + PNG_NO_SEQUENTIAL_READ + PNG_NO_WRITE_TRANSFORMS + PNG_NO_READ_ANCILLARY_CHUNKS + PNG_NO_WRITE_ANCILLARY_CHUNKS + +PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been +deprecated since libpng-1.0.16 and libpng-1.2.6. + +The function + png_check_sig(sig, num) +was replaced with + !png_sig_cmp(sig, 0, num) +It has been deprecated since libpng-0.90. + +The function + png_set_gray_1_2_4_to_8() +which also expands tRNS to alpha was replaced with + png_set_expand_gray_1_2_4_to_8() +which does not. It has been deprecated since libpng-1.0.18 and 1.2.9. + +IX. (Omitted) + + +X. Detecting libpng + +The png_get_io_ptr() function has been present since libpng-0.88, has never +changed, and is unaffected by conditional compilation macros. It is the +best choice for use in configure scripts for detecting the presence of any +libpng version since 0.88. In an autoconf "configure.in" you could use + + AC_CHECK_LIB(png, png_get_io_ptr, ... + +XI. Source code repository + +Since about February 2009, version 1.2.34, libpng has been under "git" source +control. The git repository was built from old libpng-x.y.z.tar.gz files +going back to version 0.70. You can access the git repository (read only) +at + + git://libpng.git.sourceforge.net/gitroot/libpng + +or you can browse it via "gitweb" at + + http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng + +Patches can be sent to glennrp at users.sourceforge.net or to +png-mng-implement at lists.sourceforge.net or you can upload them to +the libpng bug tracker at + + http://libpng.sourceforge.net + +XII. Coding style + +Our coding style is similar to the "Allman" style, with curly +braces on separate lines: + + if (condition) + { + action; + } + + else if (another condition) + { + another action; + } + +The braces can be omitted from simple one-line actions: + + if (condition) + return (0); + +We use 3-space indentation, except for continued statements which +are usually indented the same as the first line of the statement +plus four more spaces. + +For macro definitions we use 2-space indentation, always leaving the "#" +in the first column. + + #ifndef PNG_NO_FEATURE + # ifndef PNG_FEATURE_SUPPORTED + # define PNG_FEATURE_SUPPORTED + # endif + #endif + +Comments appear with the leading "/*" at the same indentation as +the statement that follows the comment: + + /* Single-line comment */ + statement; + + /* Multiple-line + * comment + */ + statement; + +Very short comments can be placed at the end of the statement +to which they pertain: + + statement; /* comment */ + +We don't use C++ style ("//") comments. We have, however, +used them in the past in some now-abandoned MMX assembler +code. + +Functions and their curly braces are not indented, and +exported functions are marked with PNGAPI: + + /* This is a public function that is visible to + * application programers. It does thus-and-so. + */ + void PNGAPI + png_exported_function(png_ptr, png_info, foo) + { + body; + } + +The prototypes for all exported functions appear in png.h, +above the comment that says + + /* Maintainer: Put new public prototypes here ... */ + +We mark all non-exported functions with "/* PRIVATE */"": + + void /* PRIVATE */ + png_non_exported_function(png_ptr, png_info, foo) + { + body; + } + +The prototypes for non-exported functions (except for those in +pngtest) appear in +the PNG_INTERNAL section of png.h +above the comment that says + + /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */ + +The names of all exported functions and variables begin +with "png_", and all publicly visible C preprocessor +macros begin with "PNG_". + +We put a space after each comma and after each semicolon +in "for" statments, and we put spaces before and after each +C binary operator and after "for" or "while". We don't +put a space between a typecast and the expression being +cast, nor do we put one between a function name and the +left parenthesis that follows it: + + for (i = 2; i > 0; --i) + y[i] = a(x) + (int)b; + +We prefer #ifdef and #ifndef to #if defined() and if !defined() +when there is only one macro being tested. + +We do not use the TAB character for indentation in the C sources. + +Lines do not exceed 80 characters. + +Other rules can be inferred by inspecting the libpng source. + +XIII. Y2K Compliance in libpng + +July 9, 2011 + +Since the PNG Development group is an ad-hoc body, we can't make +an official declaration. + +This is your unofficial assurance that libpng from version 0.71 and +upward through 1.2.46 are Y2K compliant. It is my belief that earlier +versions were also Y2K compliant. + +Libpng only has three year fields. One is a 2-byte unsigned integer that +will hold years up to 65535. The other two hold the date in text +format, and will hold years up to 9999. + +The integer is + "png_uint_16 year" in png_time_struct. + +The strings are + "png_charp time_buffer" in png_struct and + "near_time_buffer", which is a local character string in png.c. + +There are seven time-related functions: + + png_convert_to_rfc_1123() in png.c + (formerly png_convert_to_rfc_1152() in error) + png_convert_from_struct_tm() in pngwrite.c, called + in pngwrite.c + png_convert_from_time_t() in pngwrite.c + png_get_tIME() in pngget.c + png_handle_tIME() in pngrutil.c, called in pngread.c + png_set_tIME() in pngset.c + png_write_tIME() in pngwutil.c, called in pngwrite.c + +All appear to handle dates properly in a Y2K environment. The +png_convert_from_time_t() function calls gmtime() to convert from system +clock time, which returns (year - 1900), which we properly convert to +the full 4-digit year. There is a possibility that applications using +libpng are not passing 4-digit years into the png_convert_to_rfc_1123() +function, or that they are incorrectly passing only a 2-digit year +instead of "year - 1900" into the png_convert_from_struct_tm() function, +but this is not under our control. The libpng documentation has always +stated that it works with 4-digit years, and the APIs have been +documented as such. + +The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned +integer to hold the year, and can hold years as large as 65535. + +zlib, upon which libpng depends, is also Y2K compliant. It contains +no date-related code. + + + Glenn Randers-Pehrson + libpng maintainer + PNG Development Group @@ -1,6 +1,6 @@ -.TH LIBPNG 3 "June 26, 2010" +.TH LIBPNG 3 "July 9, 2011" .SH NAME -libpng \- Portable Network Graphics (PNG) Reference Library 1.2.44 +libpng \- Portable Network Graphics (PNG) Reference Library 1.2.46 .SH SYNOPSIS \fI\fB @@ -821,7 +821,7 @@ Following is a copy of the libpng.txt file that accompanies libpng. .SH LIBPNG.TXT libpng.txt - A description on how to use and modify libpng - libpng version 1.2.44 - June 26, 2010 + libpng version 1.2.46 - July 9, 2011 Updated and distributed by Glenn Randers-Pehrson <glennrp at users.sourceforge.net> Copyright (c) 1998-2009 Glenn Randers-Pehrson @@ -832,7 +832,7 @@ libpng.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.2.44 - June 26, 2010 + libpng versions 0.97, January 1998, through 1.2.46 - July 9, 2011 Updated and distributed by Glenn Randers-Pehrson Copyright (c) 1998-2009 Glenn Randers-Pehrson @@ -1699,7 +1699,7 @@ things. As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was added. It expands the sample depth without changing tRNS to alpha. -As of libpng version 1.2.44, not all possible expansions are supported. +As of libpng version 1.2.46, not all possible expansions are supported. In the following table, the 01 means grayscale with depth<8, 31 means indexed with depth<8, other numerals represent the color type, "T" means @@ -4000,13 +4000,13 @@ Other rules can be inferred by inspecting the libpng source. .SH XIII. Y2K Compliance in libpng -June 26, 2010 +July 9, 2011 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. This is your unofficial assurance that libpng from version 0.71 and -upward through 1.2.44 are Y2K compliant. It is my belief that earlier +upward through 1.2.46 are Y2K compliant. It is my belief that earlier versions were also Y2K compliant. Libpng only has three year fields. One is a 2-byte unsigned integer that @@ -4275,7 +4275,7 @@ the first widely used release: 1.2.37beta01-03 13 10237 12.so.0.37[.0] 1.2.37rc01 13 10237 12.so.0.37[.0] 1.2.37 13 10237 12.so.0.37[.0] - 1.2.45 10 10045 12.so.0.45[.0] + 1.0.45 10 10045 12.so.0.45[.0] 1.0.46 10 10046 10.so.0.46[.0] 1.2.38beta01 13 10238 12.so.0.38[.0] 1.2.38rc01-03 13 10238 12.so.0.38[.0] @@ -4307,6 +4307,14 @@ the first widely used release: 1.2.44beta01-03 13 10244 12.so.0.44[.0] 1.2.44rc01-03 13 10244 12.so.0.44[.0] 1.2.44 13 10244 12.so.0.44[.0] + 1.2.45beta01-03 13 10245 12.so.0.45[.0] + 1.0.55rc01 10 10055 10.so.0.55[.0] + 1.2.45rc01 13 10245 12.so.0.45[.0] + 1.0.55 10 10055 10.so.0.55[.0] + 1.2.45 13 10245 12.so.0.45[.0] + 1.2.46rc01-02 13 10246 12.so.0.46[.0] + 1.0.56 10 10056 10.so.0.56[.0] + 1.2.46 13 10246 12.so.0.46[.0] Henceforth the source version will match the shared-library minor and patch numbers; the shared-library major version number will be @@ -4362,7 +4370,7 @@ possible without all of you. Thanks to Frank J. T. Wojcik for helping with the documentation. -Libpng version 1.2.44 - June 26, 2010: +Libpng version 1.2.46 - July 9, 2011: Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). @@ -4385,7 +4393,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.2.44, June 26, 2010, are +libpng versions 1.2.6, August 15, 2004, through 1.2.46, July 9, 2011, are Copyright (c) 2004,2006-2008 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -4484,7 +4492,7 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -June 26, 2010 +July 9, 2011 .\" end of man page @@ -1,6 +1,6 @@ -.TH LIBPNGPF 3 "June 26, 2010" +.TH LIBPNGPF 3 "July 9, 2011" .SH NAME -libpng \- Portable Network Graphics (PNG) Reference Library 1.2.44 +libpng \- Portable Network Graphics (PNG) Reference Library 1.2.46 (private functions) .SH SYNOPSIS \fB#include <png.h>\fP @@ -1,4 +1,4 @@ -.TH PNG 5 "June 26, 2010" +.TH PNG 5 "July 9, 2011" .SH NAME png \- Portable Network Graphics (PNG) format .SH DESCRIPTION @@ -1,8 +1,8 @@ /* png.c - location for general purpose libpng functions * - * Last changed in libpng 1.2.43 [February 25, 2010] - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * Last changed in libpng 1.2.46 [February 25, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -17,7 +17,7 @@ #include "png.h" /* Generate a compiler error if there is an old png.h in the search path. */ -typedef version_1_2_44 Your_png_h_is_not_version_1_2_44; +typedef version_1_2_46 Your_png_h_is_not_version_1_2_46; /* Version information for C files. This had better match the version * string defined in png.h. @@ -724,14 +724,14 @@ png_get_copyright(png_structp png_ptr) #else #ifdef __STDC__ return ((png_charp) PNG_STRING_NEWLINE \ - "libpng version 1.2.44 - June 26, 2010" PNG_STRING_NEWLINE \ - "Copyright (c) 1998-2010 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \ + "libpng version 1.2.46 - July 9, 2011" PNG_STRING_NEWLINE \ + "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \ "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \ "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \ PNG_STRING_NEWLINE); #else - return ((png_charp) "libpng version 1.2.44 - June 26, 2010\ - Copyright (c) 1998-2010 Glenn Randers-Pehrson\ + return ((png_charp) "libpng version 1.2.46 - July 9, 2011\ + Copyright (c) 1998-2011 Glenn Randers-Pehrson\ Copyright (c) 1996-1997 Andreas Dilger\ Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc."); #endif @@ -1,7 +1,7 @@ /* png.h - header file for PNG reference library * - * libpng version 1.2.44 - June 26, 2010 - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * libpng version 1.2.46 - July 9, 2011 + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -10,7 +10,7 @@ * Authors and maintainers: * libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat * libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger - * libpng versions 0.97, January 1998, through 1.2.44 - June 26, 2010: Glenn + * libpng versions 0.97, January 1998, through 1.2.46 - July 9, 2011: Glenn * See also "Contributing Authors", below. * * Note about libpng version numbers: @@ -231,7 +231,7 @@ * 1.2.37beta01-03 13 10237 12.so.0.37[.0] * 1.2.37rc01 13 10237 12.so.0.37[.0] * 1.2.37 13 10237 12.so.0.37[.0] - * 1.2.45 10 10045 12.so.0.45[.0] + * 1.0.45 10 10045 12.so.0.45[.0] * 1.0.46 10 10046 10.so.0.46[.0] * 1.2.38beta01 13 10238 12.so.0.38[.0] * 1.2.38rc01-03 13 10238 12.so.0.38[.0] @@ -262,6 +262,14 @@ * 1.2.44beta01-03 13 10244 12.so.0.44[.0] * 1.2.44rc01-03 13 10244 12.so.0.44[.0] * 1.2.44 13 10244 12.so.0.44[.0] + * 1.2.45beta01-03 13 10245 12.so.0.45[.0] + * 1.0.55rc01 10 10055 10.so.0.55[.0] + * 1.2.45rc01 13 10245 12.so.0.45[.0] + * 1.0.55 10 10055 10.so.0.55[.0] + * 1.2.45 13 10245 12.so.0.45[.0] + * 1.2.46rc01-02 13 10246 12.so.0.46[.0] + * 1.0.56 10 10056 10.so.0.56[.0] + * 1.2.46 13 10246 12.so.0.46[.0] * * Henceforth the source version will match the shared-library major * and minor numbers; the shared-library major version number will be @@ -293,8 +301,8 @@ * * This code is released under the libpng license. * - * libpng versions 1.2.6, August 15, 2004, through 1.2.44, June 26, 2010, are - * Copyright (c) 2004, 2006-2010 Glenn Randers-Pehrson, and are + * libpng versions 1.2.6, August 15, 2004, through 1.2.46, July 9, 2011, are + * Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are * distributed according to the same disclaimer and license as libpng-1.2.5 * with the following individual added to the list of Contributing Authors: * @@ -405,13 +413,13 @@ * Y2K compliance in libpng: * ========================= * - * June 26, 2010 + * July 9, 2011 * * Since the PNG Development group is an ad-hoc body, we can't make * an official declaration. * * This is your unofficial assurance that libpng from version 0.71 and - * upward through 1.2.44 are Y2K compliant. It is my belief that earlier + * upward through 1.2.46 are Y2K compliant. It is my belief that earlier * versions were also Y2K compliant. * * Libpng only has three year fields. One is a 2-byte unsigned integer @@ -467,9 +475,9 @@ */ /* Version information for png.h - this should match the version in png.c */ -#define PNG_LIBPNG_VER_STRING "1.2.44" +#define PNG_LIBPNG_VER_STRING "1.2.46" #define PNG_HEADER_VERSION_STRING \ - " libpng version 1.2.44 - June 26, 2010\n" + " libpng version 1.2.46 - July 9, 2011\n" #define PNG_LIBPNG_VER_SONUM 0 #define PNG_LIBPNG_VER_DLLNUM 13 @@ -477,7 +485,7 @@ /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */ #define PNG_LIBPNG_VER_MAJOR 1 #define PNG_LIBPNG_VER_MINOR 2 -#define PNG_LIBPNG_VER_RELEASE 44 +#define PNG_LIBPNG_VER_RELEASE 46 /* This should match the numeric part of the final component of * PNG_LIBPNG_VER_STRING, omitting any leading zero: */ @@ -507,7 +515,7 @@ * version 1.0.0 was mis-numbered 100 instead of 10000). From * version 1.0.1 it's xxyyzz, where x=major, y=minor, z=release */ -#define PNG_LIBPNG_VER 10244 /* 1.2.44 */ +#define PNG_LIBPNG_VER 10246 /* 1.2.46 */ #ifndef PNG_VERSION_INFO_ONLY /* Include the compression library's header */ @@ -1600,7 +1608,7 @@ struct png_struct_def /* This triggers a compiler error in png.c, if png.c and png.h * do not agree upon the version number. */ -typedef png_structp version_1_2_44; +typedef png_structp version_1_2_46; typedef png_struct FAR * FAR * png_structpp; @@ -1,8 +1,8 @@ /* pngconf.h - machine configurable file for libpng * - * libpng version 1.2.44 - June 26, 2010 - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * libpng version 1.2.46 - July 9, 2011 + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -1,8 +1,8 @@ /* pngerror.c - stub functions for i/o and memory allocation * - * Last changed in libpng 1.2.41 [December 3, 2009] - * Copyright (c) 1998-2009 Glenn Randers-Pehrson + * Last changed in libpng 1.2.45 [July 7, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -87,12 +87,17 @@ png_error(png_structp png_ptr, png_const_charp error_message) void PNGAPI png_err(png_structp png_ptr) { + /* Prior to 1.2.45 the error_fn received a NULL pointer, expressed + * erroneously as '\0', instead of the empty string "". This was + * apparently an error, introduced in libpng-1.2.20, and png_default_error + * will crash in this case. + */ if (png_ptr != NULL && png_ptr->error_fn != NULL) - (*(png_ptr->error_fn))(png_ptr, '\0'); + (*(png_ptr->error_fn))(png_ptr, ""); /* If the custom handler doesn't exist, or if it returns, use the default handler, which will not return. */ - png_default_error(png_ptr, '\0'); + png_default_error(png_ptr, ""); } #endif /* PNG_ERROR_TEXT_SUPPORTED */ @@ -181,8 +186,13 @@ png_format_buffer(png_structp png_ptr, png_charp buffer, png_const_charp { buffer[iout++] = ':'; buffer[iout++] = ' '; - png_memcpy(buffer + iout, error_message, PNG_MAX_ERROR_TEXT); - buffer[iout + PNG_MAX_ERROR_TEXT - 1] = '\0'; + + iin = 0; + while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0') + buffer[iout++] = error_message[iin++]; + + /* iin < PNG_MAX_ERROR_TEXT, so the following is safe: */ + buffer[iout] = '\0'; } } @@ -442,7 +442,7 @@ png_destroy_struct_2(png_voidp struct_ptr, png_free_ptr free_fn, * have the ability to do that. */ -png_voidp PNGAPI +png_voidp /* PRIVATE */ png_calloc(png_structp png_ptr, png_uint_32 size) { png_voidp ret; @@ -1,8 +1,8 @@ /* pngrtran.c - transforms the data in a row for PNG readers * - * Last changed in libpng 1.2.43 [February 25, 2010] - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * Last changed in libpng 1.2.45 [July 7, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -676,10 +676,21 @@ void PNGAPI png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red, double green) { - int red_fixed = (int)((float)red*100000.0 + 0.5); - int green_fixed = (int)((float)green*100000.0 + 0.5); + int red_fixed, green_fixed; if (png_ptr == NULL) return; + if (red > 21474.83647 || red < -21474.83648 || + green > 21474.83647 || green < -21474.83648) + { + png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients"); + red_fixed = -1; + green_fixed = -1; + } + else + { + red_fixed = (int)((float)red*100000.0 + 0.5); + green_fixed = (int)((float)green*100000.0 + 0.5); + } png_set_rgb_to_gray_fixed(png_ptr, error_action, red_fixed, green_fixed); } #endif @@ -1196,8 +1207,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr) { if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) { - if (png_ptr->num_trans && - (png_ptr->transformations & PNG_EXPAND_tRNS)) + if (png_ptr->num_trans) info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA; else info_ptr->color_type = PNG_COLOR_TYPE_RGB; @@ -1,8 +1,8 @@ /* pngrutil.c - utilities to read a PNG file * - * Last changed in libpng 1.2.44 [June 26, 2010] - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * Last changed in libpng 1.2.45 [July 7, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -1829,6 +1829,14 @@ png_handle_sCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length) return; } + /* Need unit type, width, \0, height: minimum 4 bytes */ + else if (length < 4) + { + png_warning(png_ptr, "sCAL chunk too short"); + png_crc_finish(png_ptr, length); + return; + } + png_debug1(2, "Allocating and reading sCAL chunk data (%lu bytes)", length + 1); png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1); @@ -1702,4 +1702,4 @@ main(int argc, char *argv[]) } /* Generate a compiler error if there is an old png.h in the search path. */ -typedef version_1_2_44 your_png_h_is_not_version_1_2_44; +typedef version_1_2_46 your_png_h_is_not_version_1_2_46; @@ -1,8 +1,8 @@ /* pngwrite.c - general routines to write a PNG file * - * Last changed in libpng 1.2.42 [January 3, 2010] - * Copyright (c) 1998-2010 Glenn Randers-Pehrson + * Last changed in libpng 1.2.45 [July 7, 2011] + * Copyright (c) 1998-2011 Glenn Randers-Pehrson * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) * @@ -295,6 +295,7 @@ png_write_info(png_structp png_ptr, png_infop info_ptr) if (keep != PNG_HANDLE_CHUNK_NEVER && up->location && (up->location & PNG_HAVE_PLTE) && !(up->location & PNG_HAVE_IDAT) && + !(up->location & PNG_AFTER_IDAT) && ((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS || (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS))) { diff --git a/projects/wince.txt b/projects/wince.txt index c59ec88..b35e101 100644 --- a/projects/wince.txt +++ b/projects/wince.txt @@ -1,6 +1,6 @@ A set of project files is available for WinCE. Get -libpng-1.2.44-project-wince.zip from a libpng distribution +libpng-1.2.46-project-wince.zip from a libpng distribution site such as http://libpng.sourceforge.net/index.html Put the zip file in this directory (projects) and then run -"unzip -a libpng-1.2.44-project-wince.zip" +"unzip -a libpng-1.2.46-project-wince.zip" diff --git a/projects/xcode/libpng.xcodeproj/project.pbxproj b/projects/xcode/libpng.xcodeproj/project.pbxproj index c2eb468..fb4d90a 100644 --- a/projects/xcode/libpng.xcodeproj/project.pbxproj +++ b/projects/xcode/libpng.xcodeproj/project.pbxproj @@ -222,7 +222,7 @@ COPY_PHASE_STRIP = NO; DYLIB_COMPATIBILITY_VERSION = 3; DYLIB_CURRENT_VERSION = 3; - FRAMEWORK_VERSION = 1.2.44; + FRAMEWORK_VERSION = 1.2.46; GCC_PRECOMPILE_PREFIX_HEADER = NO; GCC_PREFIX_HEADER = ""; INFOPLIST_FILE = Info.plist; @@ -240,7 +240,7 @@ buildSettings = { DYLIB_COMPATIBILITY_VERSION = 3; DYLIB_CURRENT_VERSION = 3; - FRAMEWORK_VERSION = 1.2.44; + FRAMEWORK_VERSION = 1.2.46; GCC_PRECOMPILE_PREFIX_HEADER = NO; GCC_PREFIX_HEADER = ""; INFOPLIST_FILE = Info.plist; diff --git a/scripts/README.txt b/scripts/README.txt index a6f33e9..177b22c 100644 --- a/scripts/README.txt +++ b/scripts/README.txt @@ -1,8 +1,8 @@ -Makefiles for libpng version 1.2.44 - June 26, 2010 +Makefiles for libpng version 1.2.46 - July 9, 2011 makefile.linux => Linux/ELF makefile - (gcc, creates libpng12.so.0.1.2.44) + (gcc, creates libpng12.so.0.1.2.46) makefile.gcc => Generic makefile (gcc, creates static libpng.a) makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr (Requires ansi2knr.c from @@ -20,7 +20,7 @@ Makefiles for libpng version 1.2.44 - June 26, 2010 makefile.dec => DEC Alpha UNIX makefile makefile.dj2 => DJGPP 2 makefile makefile.elf => Linux/ELF makefile symbol versioning, - gcc, creates libpng12.so.0.1.2.44) + gcc, creates libpng12.so.0.1.2.46) makefile.freebsd => FreeBSD makefile makefile.gcc => Generic gcc makefile makefile.gccmmx => Generic gcc makefile previously using MMX code @@ -38,14 +38,14 @@ Makefiles for libpng version 1.2.44 - June 26, 2010 makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def) makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc makefile.sggcc => Silicon Graphics (gcc, - creates libpng12.so.0.1.2.44) + creates libpng12.so.0.1.2.46) makefile.sgi => Silicon Graphics IRIX makefile (cc, creates static lib) makefile.solaris => Solaris 2.X makefile (gcc, - creates libpng12.so.0.1.2.44) + creates libpng12.so.0.1.2.46) makefile.solaris-x86 => Solaris 2.X makefile (gcc, no MMX code, - creates libpng12.so.0.1.2.44) + creates libpng12.so.0.1.2.46) makefile.so9 => Solaris 9 makefile (gcc, - creates libpng12.so.0.1.2.44) + creates libpng12.so.0.1.2.46) makefile.std => Generic UNIX makefile (cc, creates static libpng.a) makefile.sunos => Sun makefile makefile.32sunu => Sun Ultra 32-bit makefile diff --git a/scripts/libpng-config-head.in b/scripts/libpng-config-head.in index 82e0fdd..82ab821 100755 --- a/scripts/libpng-config-head.in +++ b/scripts/libpng-config-head.in @@ -11,7 +11,7 @@ # Modeled after libxml-config. -version=1.2.44 +version=1.2.46 prefix="" libdir="" libs="" diff --git a/scripts/libpng.pc.in b/scripts/libpng.pc.in index 9a30534..2a108fc 100644 --- a/scripts/libpng.pc.in +++ b/scripts/libpng.pc.in @@ -5,6 +5,6 @@ includedir=@includedir@/libpng12 Name: libpng Description: Loads and saves PNG files -Version: 1.2.44 +Version: 1.2.46 Libs: -L${libdir} -lpng12 Cflags: -I${includedir} diff --git a/scripts/makefile.32sunu b/scripts/makefile.32sunu index db0f3e5..670a9c8 100644 --- a/scripts/makefile.32sunu +++ b/scripts/makefile.32sunu @@ -11,7 +11,7 @@ # Library name: LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.64sunu b/scripts/makefile.64sunu index e7e5317..3771665 100644 --- a/scripts/makefile.64sunu +++ b/scripts/makefile.64sunu @@ -11,7 +11,7 @@ # Library name: LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.aix b/scripts/makefile.aix index 6be3f0c..7ef49c5 100644 --- a/scripts/makefile.aix +++ b/scripts/makefile.aix @@ -23,7 +23,7 @@ LN_SF = ln -f -s LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) prefix=/usr/local diff --git a/scripts/makefile.beos b/scripts/makefile.beos index 9c0b287..19425fe 100644 --- a/scripts/makefile.beos +++ b/scripts/makefile.beos @@ -11,7 +11,7 @@ # Library name: LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.cegcc b/scripts/makefile.cegcc index f18614a..6e9cd75 100644 --- a/scripts/makefile.cegcc +++ b/scripts/makefile.cegcc @@ -23,7 +23,7 @@ VERMAJ = 1 VERMIN = 2 -VERMIC = 44 +VERMIC = 46 VER = $(VERMAJ).$(VERMIN).$(VERMIC) NAME = libpng PACKAGE = $(NAME)-$(VER) diff --git a/scripts/makefile.cygwin b/scripts/makefile.cygwin index 11ec1e5..4a1c7ad 100644 --- a/scripts/makefile.cygwin +++ b/scripts/makefile.cygwin @@ -77,7 +77,7 @@ CFLAGS= $(strip $(MINGW_CCFLAGS) $(addprefix -I,$(ZLIBINC)) \ LIBNAME = libpng12 PNGMAJ = 0 CYGDLL = 12 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) SHAREDLIB=cygpng$(CYGDLL).dll diff --git a/scripts/makefile.darwin b/scripts/makefile.darwin index ed7a8e3..5b53046 100644 --- a/scripts/makefile.darwin +++ b/scripts/makefile.darwin @@ -22,7 +22,7 @@ ZLIBINC=../zlib # Library name: LIBNAME = libpng12 PNGMAJ = 12 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.dec b/scripts/makefile.dec index c97c6e6..36bdd4f 100644 --- a/scripts/makefile.dec +++ b/scripts/makefile.dec @@ -8,7 +8,7 @@ # Library name: PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) LIBNAME = libpng12 diff --git a/scripts/makefile.elf b/scripts/makefile.elf index 2631247..705db1b 100644 --- a/scripts/makefile.elf +++ b/scripts/makefile.elf @@ -16,7 +16,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.gcmmx b/scripts/makefile.gcmmx index 833d114..c5402e9 100644 --- a/scripts/makefile.gcmmx +++ b/scripts/makefile.gcmmx @@ -17,7 +17,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.hp64 b/scripts/makefile.hp64 index 0f8b340..b693f75 100644 --- a/scripts/makefile.hp64 +++ b/scripts/makefile.hp64 @@ -21,7 +21,7 @@ ZLIBINC=/opt/zlib/include # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.hpgcc b/scripts/makefile.hpgcc index bd7d875..ff0d3c1 100644 --- a/scripts/makefile.hpgcc +++ b/scripts/makefile.hpgcc @@ -11,7 +11,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.hpux b/scripts/makefile.hpux index c24b667..6c94bad 100644 --- a/scripts/makefile.hpux +++ b/scripts/makefile.hpux @@ -21,7 +21,7 @@ ZLIBINC=/opt/zlib/include # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.linux b/scripts/makefile.linux index faf697f..5621260 100644 --- a/scripts/makefile.linux +++ b/scripts/makefile.linux @@ -10,7 +10,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.mingw b/scripts/makefile.mingw index 1d7444e..caf9469 100644 --- a/scripts/makefile.mingw +++ b/scripts/makefile.mingw @@ -81,7 +81,7 @@ CFLAGS= $(strip $(MINGW_CCFLAGS) $(addprefix -I,$(ZLIBINC)) \ LIBNAME = libpng12 PNGMAJ = 0 MINGDLL = 12 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) SHAREDLIB=libpng$(MINGDLL).dll diff --git a/scripts/makefile.ne12bsd b/scripts/makefile.ne12bsd index fa0501f..d4687da 100644 --- a/scripts/makefile.ne12bsd +++ b/scripts/makefile.ne12bsd @@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng12 LIB= png12 SHLIB_MAJOR= 0 -SHLIB_MINOR= 1.2.44 +SHLIB_MINOR= 1.2.46 SRCS= png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \ pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \ pngwtran.c pngmem.c pngerror.c pngpread.c diff --git a/scripts/makefile.netbsd b/scripts/makefile.netbsd index 47cd7df..32164c7 100644 --- a/scripts/makefile.netbsd +++ b/scripts/makefile.netbsd @@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include LIB= png SHLIB_MAJOR= 3 -SHLIB_MINOR= 1.2.44 +SHLIB_MINOR= 1.2.46 SRCS= png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \ pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \ pngwtran.c pngmem.c pngerror.c pngpread.c diff --git a/scripts/makefile.nommx b/scripts/makefile.nommx index b414433..1d2842e 100644 --- a/scripts/makefile.nommx +++ b/scripts/makefile.nommx @@ -10,7 +10,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.openbsd b/scripts/makefile.openbsd index d5cbe23..c3c2e3b 100644 --- a/scripts/makefile.openbsd +++ b/scripts/makefile.openbsd @@ -11,7 +11,7 @@ LIBDIR= ${PREFIX}/lib MANDIR= ${PREFIX}/man/cat SHLIB_MAJOR= 0 -SHLIB_MINOR= 1.2.44 +SHLIB_MINOR= 1.2.46 LIB= png SRCS= png.c pngerror.c pngget.c pngmem.c pngpread.c \ diff --git a/scripts/makefile.sco b/scripts/makefile.sco index a3c9f0f..0e59423 100644 --- a/scripts/makefile.sco +++ b/scripts/makefile.sco @@ -12,7 +12,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.sggcc b/scripts/makefile.sggcc index 28b129e..c6b3e50 100644 --- a/scripts/makefile.sggcc +++ b/scripts/makefile.sggcc @@ -9,7 +9,7 @@ # Library name: LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.sgi b/scripts/makefile.sgi index 0baa9d0..d34ea99 100644 --- a/scripts/makefile.sgi +++ b/scripts/makefile.sgi @@ -9,7 +9,7 @@ # Library name: LIBNAME=libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.so9 b/scripts/makefile.so9 index 5350af4..f202fb4 100644 --- a/scripts/makefile.so9 +++ b/scripts/makefile.so9 @@ -11,7 +11,7 @@ # Library name: PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) LIBNAME = libpng12 diff --git a/scripts/makefile.solaris b/scripts/makefile.solaris index eb65495..294b0f7 100644 --- a/scripts/makefile.solaris +++ b/scripts/makefile.solaris @@ -11,7 +11,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/makefile.solaris-x86 b/scripts/makefile.solaris-x86 index 940ff93..575d789 100644 --- a/scripts/makefile.solaris-x86 +++ b/scripts/makefile.solaris-x86 @@ -11,7 +11,7 @@ # Library name: LIBNAME = libpng12 PNGMAJ = 0 -PNGMIN = 1.2.44 +PNGMIN = 1.2.46 PNGVER = $(PNGMAJ).$(PNGMIN) # Shared library names: diff --git a/scripts/png32ce.def b/scripts/png32ce.def index 97bcdec..8b00637 100644 --- a/scripts/png32ce.def +++ b/scripts/png32ce.def @@ -5,7 +5,7 @@ LIBRARY lpngce EXPORTS -;Version 1.2.44 +;Version 1.2.46 png_build_grayscale_palette @1 png_check_sig @2 png_chunk_error @3 diff --git a/scripts/pngos2.def b/scripts/pngos2.def index 8f16fb1..e9e92f9 100644 --- a/scripts/pngos2.def +++ b/scripts/pngos2.def @@ -2,7 +2,7 @@ ; PNG.LIB module definition file for OS/2 ;---------------------------------------- -; Version 1.2.44 +; Version 1.2.46 LIBRARY PNG DESCRIPTION "PNG image compression library for OS/2" diff --git a/scripts/pngw32.def b/scripts/pngw32.def index e09e708..ba5e91a 100644 --- a/scripts/pngw32.def +++ b/scripts/pngw32.def @@ -5,7 +5,7 @@ LIBRARY EXPORTS -;Version 1.2.44 +;Version 1.2.46 png_build_grayscale_palette @1 png_check_sig @2 png_chunk_error @3 |