libpng: update to 1.2.43

I unpacked libpng 1.2.43 and did:
 cd third_party/libpng
 for x in $(ls -1) ; do cp /tmp/libpng-1.2.43/$x .; done

The diffs appear to all be safe. The Chromium specific config is in pngusr.h
and isn't touched by this change.

1.2.43 fixes http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-0205

c7013d773eb45b8ed6a864e419e544106a0dd95d  /tmp/libpng-1.2.43.tar.xz

BUG=38512
TEST=none

http://codereview.chromium.org/1118002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@41972 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 237 insertions, 162 deletions

diff --git a/third_party/libpng/pngrtran.c b/third_party/libpng/pngrtran.c
index af396df..af1aa8e 100644
--- a/third_party/libpng/pngrtran.c
+++ b/third_party/libpng/pngrtran.c
@@ -1,12 +1,15 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.2.37 [June 4, 2009]
- * For conditions of distribution and use, see copyright notice in png.h
- * Copyright (c) 1998-2009 Glenn Randers-Pehrson
+ * Last changed in libpng 1.2.43 [February 25, 2010]
+ * Copyright (c) 1998-2010 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.)
  *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ *
  * This file contains functions optionally called by an application
  * in order to tell libpng how to handle data when reading a PNG.
  * Transformations that are used in both reading and writing are
@@ -14,17 +17,20 @@
  */
 
 #define PNG_INTERNAL
+#define PNG_NO_PEDANTIC_WARNINGS
 #include "png.h"
-#if defined(PNG_READ_SUPPORTED)
+#ifdef PNG_READ_SUPPORTED
 
 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
 void PNGAPI
 png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
 {
    png_debug(1, "in png_set_crc_action");
-   /* Tell libpng how we react to CRC errors in critical chunks */
+ 
    if (png_ptr == NULL)
       return;
+
+   /* Tell libpng how we react to CRC errors in critical chunks */
    switch (crit_action)
    {
       case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
@@ -52,6 +58,7 @@ png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
          break;
    }
 
+   /* Tell libpng how we react to CRC errors in ancillary chunks */
    switch (ancil_action)
    {
       case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */
@@ -91,6 +98,7 @@ png_set_background(png_structp png_ptr,
    int need_expand, double background_gamma)
 {
    png_debug(1, "in png_set_background");
+ 
    if (png_ptr == NULL)
       return;
    if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
@@ -108,30 +116,32 @@ png_set_background(png_structp png_ptr,
 }
 #endif
 
-#if defined(PNG_READ_16_TO_8_SUPPORTED)
+#ifdef PNG_READ_16_TO_8_SUPPORTED
 /* Strip 16 bit depth files to 8 bit depth */
 void PNGAPI
 png_set_strip_16(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_16");
+
    if (png_ptr == NULL)
       return;
    png_ptr->transformations |= PNG_16_TO_8;
 }
 #endif
 
-#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
 void PNGAPI
 png_set_strip_alpha(png_structp png_ptr)
 {
    png_debug(1, "in png_set_strip_alpha");
+
    if (png_ptr == NULL)
       return;
    png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
 }
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED)
+#ifdef PNG_READ_DITHER_SUPPORTED
 /* Dither file to 8 bit.  Supply a palette, the current number
  * of elements in the palette, the maximum number of elements
  * allowed, and a histogram if possible.  If the current number
@@ -156,6 +166,7 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
    int full_dither)
 {
    png_debug(1, "in png_set_dither");
+
    if (png_ptr == NULL)
       return;
    png_ptr->transformations |= PNG_DITHER;
@@ -325,9 +336,8 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
             png_ptr->palette_to_index[i] = (png_byte)i;
          }
 
-         hash = (png_dsortpp)png_malloc(png_ptr, (png_uint_32)(769 *
+         hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
             png_sizeof(png_dsortp)));
-         png_memset(hash, 0, 769 * png_sizeof(png_dsortp));
 
          num_new_palette = num_palette;
 
@@ -422,8 +432,10 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
                         png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
                            = png_ptr->palette_to_index[num_new_palette];
 
-                        png_ptr->index_to_palette[j] = (png_byte)num_new_palette;
-                        png_ptr->palette_to_index[num_new_palette] = (png_byte)j;
+                        png_ptr->index_to_palette[j] =
+                            (png_byte)num_new_palette;
+                        png_ptr->palette_to_index[num_new_palette] =
+                            (png_byte)j;
                      }
                      if (num_new_palette <= maximum_colors)
                         break;
@@ -473,14 +485,12 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
       int num_green = (1 << PNG_DITHER_GREEN_BITS);
       int num_blue = (1 << PNG_DITHER_BLUE_BITS);
       png_size_t num_entries = ((png_size_t)1 << total_bits);
-      png_ptr->palette_lookup = (png_bytep )png_malloc(png_ptr,
+
+      png_ptr->palette_lookup = (png_bytep )png_calloc(png_ptr,
          (png_uint_32)(num_entries * png_sizeof(png_byte)));
-      png_memset(png_ptr->palette_lookup, 0, num_entries *
-         png_sizeof(png_byte));
 
       distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
          png_sizeof(png_byte)));
-
       png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
 
       for (i = 0; i < num_palette; i++)
@@ -494,7 +504,8 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
          {
             /* int dr = abs(ir - r); */
             int dr = ((ir > r) ? ir - r : r - ir);
-            int index_r = (ir << (PNG_DITHER_BLUE_BITS + PNG_DITHER_GREEN_BITS));
+            int index_r = (ir << (PNG_DITHER_BLUE_BITS +
+                PNG_DITHER_GREEN_BITS));
 
             for (ig = 0; ig < num_green; ig++)
             {
@@ -541,8 +552,10 @@ void PNGAPI
 png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
 {
    png_debug(1, "in png_set_gamma");
+
    if (png_ptr == NULL)
       return;
+
    if ((fabs(scrn_gamma * file_gamma - 1.0) > PNG_GAMMA_THRESHOLD) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
        (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
@@ -552,7 +565,7 @@ png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
 }
 #endif
 
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+#ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expand paletted images to RGB, expand grayscale images of
  * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
  * to alpha channels.
@@ -561,8 +574,10 @@ void PNGAPI
 png_set_expand(png_structp png_ptr)
 {
    png_debug(1, "in png_set_expand");
+
    if (png_ptr == NULL)
       return;
+
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
@@ -580,8 +595,9 @@ png_set_expand(png_structp png_ptr)
  *  More to the point, these functions make it obvious what libpng will be
  *  doing, whereas "expand" can (and does) mean any number of things.
  *
- *  GRP 20060307: In libpng-1.4.0, png_set_gray_1_2_4_to_8() was modified
- *  to expand only the sample depth but not to expand the tRNS to alpha.
+ *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
+ *  to expand only the sample depth but not to expand the tRNS to alpha
+ *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
  */
 
 /* Expand paletted images to RGB. */
@@ -589,20 +605,24 @@ void PNGAPI
 png_set_palette_to_rgb(png_structp png_ptr)
 {
    png_debug(1, "in png_set_palette_to_rgb");
+
    if (png_ptr == NULL)
       return;
+
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 
-#if !defined(PNG_1_0_X)
+#ifndef PNG_1_0_X
 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
 void PNGAPI
 png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
 {
    png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
+
    if (png_ptr == NULL)
       return;
+
    png_ptr->transformations |= PNG_EXPAND;
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
@@ -615,8 +635,10 @@ void PNGAPI
 png_set_gray_1_2_4_to_8(png_structp png_ptr)
 {
    png_debug(1, "in png_set_gray_1_2_4_to_8");
+
    if (png_ptr == NULL)
       return;
+
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
 }
 #endif
@@ -627,23 +649,25 @@ void PNGAPI
 png_set_tRNS_to_alpha(png_structp png_ptr)
 {
    png_debug(1, "in png_set_tRNS_to_alpha");
+
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 void PNGAPI
 png_set_gray_to_rgb(png_structp png_ptr)
 {
    png_debug(1, "in png_set_gray_to_rgb");
+
    png_ptr->transformations |= PNG_GRAY_TO_RGB;
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
 }
 #endif
 
-#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
-#if defined(PNG_FLOATING_POINT_SUPPORTED)
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+#ifdef PNG_FLOATING_POINT_SUPPORTED
 /* Convert a RGB image to a grayscale of the same width.  This allows us,
  * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
  */
@@ -665,8 +689,10 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
    png_fixed_point red, png_fixed_point green)
 {
    png_debug(1, "in png_set_rgb_to_gray");
+
    if (png_ptr == NULL)
       return;
+
    switch(error_action)
    {
       case 1: png_ptr->transformations |= PNG_RGB_TO_GRAY;
@@ -678,7 +704,7 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
       case 3: png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
    }
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+#ifdef PNG_READ_EXPAND_SUPPORTED
       png_ptr->transformations |= PNG_EXPAND;
 #else
    {
@@ -714,16 +740,18 @@ png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
 #endif
 
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
-    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED) || \
-    defined(PNG_LEGACY_SUPPORTED)
+    defined(PNG_LEGACY_SUPPORTED) || \
+    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
 void PNGAPI
 png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
    read_user_transform_fn)
 {
    png_debug(1, "in png_set_read_user_transform_fn");
+
    if (png_ptr == NULL)
       return;
-#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
+
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    png_ptr->transformations |= PNG_USER_TRANSFORM;
    png_ptr->read_user_transform_fn = read_user_transform_fn;
 #endif
@@ -742,18 +770,20 @@ void /* PRIVATE */
 png_init_read_transformations(png_structp png_ptr)
 {
    png_debug(1, "in png_init_read_transformations");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
-   if (png_ptr != NULL)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
+  if (png_ptr != NULL)
 #endif
   {
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || defined(PNG_READ_SHIFT_SUPPORTED) \
- || defined(PNG_READ_GAMMA_SUPPORTED)
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
+    defined(PNG_READ_SHIFT_SUPPORTED) || \
+    defined(PNG_READ_GAMMA_SUPPORTED)
    int color_type = png_ptr->color_type;
 #endif
 
 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* Detect gray background and attempt to enable optimization
     * for gray --> RGB case
     *
@@ -840,10 +870,10 @@ png_init_read_transformations(png_structp png_ptr)
          png_ptr->background.blue  =
             png_ptr->palette[png_ptr->background.index].blue;
 
-#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
         if (png_ptr->transformations & PNG_INVERT_ALPHA)
         {
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+#ifdef PNG_READ_EXPAND_SUPPORTED
            if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
 #endif
            {
@@ -886,7 +916,8 @@ png_init_read_transformations(png_structp png_ptr)
         png_ptr->gamma != 0.0)
    {
       png_build_gamma_table(png_ptr);
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
       if (png_ptr->transformations & PNG_BACKGROUND)
       {
          if (color_type == PNG_COLOR_TYPE_PALETTE)
@@ -943,7 +974,8 @@ png_init_read_transformations(png_structp png_ptr)
                   back.red = (png_byte)(pow(
                      (double)png_ptr->background.red/255, gs) * 255.0 + .5);
                   back.green = (png_byte)(pow(
-                     (double)png_ptr->background.green/255, gs) * 255.0 + .5);
+                     (double)png_ptr->background.green/255, gs) * 255.0
+                         + .5);
                   back.blue = (png_byte)(pow(
                      (double)png_ptr->background.blue/255, gs) * 255.0 + .5);
                }
@@ -987,14 +1019,14 @@ png_init_read_transformations(png_structp png_ptr)
                   palette[i].blue = png_ptr->gamma_table[palette[i].blue];
                }
             }
-	    /* Prevent the transformations being done again, and make sure
-	     * that the now spurious alpha channel is stripped - the code
-	     * has just reduced background composition and gamma correction
-	     * to a simple alpha channel strip.
-	     */
-	    png_ptr->transformations &= ~PNG_BACKGROUND;
-	    png_ptr->transformations &= ~PNG_GAMMA;
-	    png_ptr->transformations |= PNG_STRIP_ALPHA;
+            /* Prevent the transformations being done again, and make sure
+             * that the now spurious alpha channel is stripped - the code
+             * has just reduced background composition and gamma correction
+             * to a simple alpha channel strip.
+             */
+            png_ptr->transformations &= ~PNG_BACKGROUND;
+            png_ptr->transformations &= ~PNG_GAMMA;
+            png_ptr->transformations |= PNG_STRIP_ALPHA;
          }
          /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
          else
@@ -1072,15 +1104,15 @@ png_init_read_transformations(png_structp png_ptr)
             palette[i].blue = png_ptr->gamma_table[palette[i].blue];
          }
 
-	 /* Done the gamma correction. */
-	 png_ptr->transformations &= ~PNG_GAMMA;
+         /* Done the gamma correction. */
+         png_ptr->transformations &= ~PNG_GAMMA;
       }
    }
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    else
 #endif
 #endif /* PNG_READ_GAMMA_SUPPORTED && PNG_FLOATING_POINT_SUPPORTED */
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    /* No GAMMA transformation */
    if ((png_ptr->transformations & PNG_BACKGROUND) &&
        (color_type == PNG_COLOR_TYPE_PALETTE))
@@ -1118,7 +1150,7 @@ png_init_read_transformations(png_structp png_ptr)
    }
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
 
-#if defined(PNG_READ_SHIFT_SUPPORTED)
+#ifdef PNG_READ_SHIFT_SUPPORTED
    if ((png_ptr->transformations & PNG_SHIFT) &&
       (color_type == PNG_COLOR_TYPE_PALETTE))
    {
@@ -1158,7 +1190,8 @@ void /* PRIVATE */
 png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
 {
    png_debug(1, "in png_read_transform_info");
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+
+#ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
       if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
@@ -1177,10 +1210,6 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
          {
             if (png_ptr->transformations & PNG_EXPAND_tRNS)
               info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
-#if 0 /* Removed from libpng-1.2.27 */
-            else
-              info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
-#endif
          }
          if (info_ptr->bit_depth < 8)
             info_ptr->bit_depth = 8;
@@ -1189,7 +1218,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    }
 #endif
 
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    if (png_ptr->transformations & PNG_BACKGROUND)
    {
       info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
@@ -1198,7 +1227,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    }
 #endif
 
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
    if (png_ptr->transformations & PNG_GAMMA)
    {
 #ifdef PNG_FLOATING_POINT_SUPPORTED
@@ -1210,22 +1239,22 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    }
 #endif
 
-#if defined(PNG_READ_16_TO_8_SUPPORTED)
+#ifdef PNG_READ_16_TO_8_SUPPORTED
    if ((png_ptr->transformations & PNG_16_TO_8) && (info_ptr->bit_depth == 16))
       info_ptr->bit_depth = 8;
 #endif
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
       info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
 #endif
 
-#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
       info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED)
+#ifdef PNG_READ_DITHER_SUPPORTED
    if (png_ptr->transformations & PNG_DITHER)
    {
       if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
@@ -1237,7 +1266,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    }
 #endif
 
-#if defined(PNG_READ_PACK_SUPPORTED)
+#ifdef PNG_READ_PACK_SUPPORTED
    if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
       info_ptr->bit_depth = 8;
 #endif
@@ -1249,7 +1278,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    else
       info_ptr->channels = 1;
 
-#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
       info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
 #endif
@@ -1257,7 +1286,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
       info_ptr->channels++;
 
-#if defined(PNG_READ_FILLER_SUPPORTED)
+#ifdef PNG_READ_FILLER_SUPPORTED
    /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
    if ((png_ptr->transformations & PNG_FILLER) &&
        ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
@@ -1265,7 +1294,7 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
    {
       info_ptr->channels++;
       /* If adding a true alpha channel not just filler */
-#if !defined(PNG_1_0_X)
+#ifndef PNG_1_0_X
       if (png_ptr->transformations & PNG_ADD_ALPHA)
         info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
 #endif
@@ -1288,7 +1317,7 @@ defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
 
    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
 
-#if !defined(PNG_READ_EXPAND_SUPPORTED)
+#ifndef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr)
       return;
 #endif
@@ -1302,9 +1331,10 @@ void /* PRIVATE */
 png_do_read_transformations(png_structp png_ptr)
 {
    png_debug(1, "in png_do_read_transformations");
+
    if (png_ptr->row_buf == NULL)
    {
-#if !defined(PNG_NO_STDIO) && !defined(_WIN32_WCE)
+#if defined(PNG_STDIO_SUPPORTED) && !defined(_WIN32_WCE)
       char msg[50];
 
       png_snprintf2(msg, 50,
@@ -1328,7 +1358,7 @@ png_do_read_transformations(png_structp png_ptr)
 #endif
 #endif
 
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+#ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
       if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
@@ -1349,17 +1379,18 @@ png_do_read_transformations(png_structp png_ptr)
    }
 #endif
 
-#if defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
       png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
          PNG_FLAG_FILLER_AFTER | (png_ptr->flags & PNG_FLAG_STRIP_ALPHA));
 #endif
 
-#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
    {
       int rgb_error =
-         png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info), png_ptr->row_buf + 1);
+         png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info),
+             png_ptr->row_buf + 1);
       if (rgb_error)
       {
          png_ptr->rgb_to_gray_status=1;
@@ -1374,12 +1405,12 @@ png_do_read_transformations(png_structp png_ptr)
 #endif
 
 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
- * 
+ *
  *   In most cases, the "simple transparency" should be done prior to doing
  *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
  *   pixel is transparent.  You would also need to make sure that the
  *   transparency information is upgraded to RGB.
- * 
+ *
  *   To summarize, the current flow is:
  *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
  *                                   with background "in place" if transparent,
@@ -1404,7 +1435,7 @@ png_do_read_transformations(png_structp png_ptr)
  *  transform appropriately, then it would save a lot of work/time.
  */
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if background is non-gray; else do later
     * for performance reasons
     */
@@ -1413,13 +1444,13 @@ png_do_read_transformations(png_structp png_ptr)
       png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    if ((png_ptr->transformations & PNG_BACKGROUND) &&
       ((png_ptr->num_trans != 0 ) ||
       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)))
       png_do_background(&(png_ptr->row_info), png_ptr->row_buf + 1,
          &(png_ptr->trans_values), &(png_ptr->background)
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
          , &(png_ptr->background_1),
          png_ptr->gamma_table, png_ptr->gamma_from_1,
          png_ptr->gamma_to_1, png_ptr->gamma_16_table,
@@ -1429,9 +1460,9 @@ png_do_read_transformations(png_structp png_ptr)
 );
 #endif
 
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
    if ((png_ptr->transformations & PNG_GAMMA) &&
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
        !((png_ptr->transformations & PNG_BACKGROUND) &&
        ((png_ptr->num_trans != 0) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
@@ -1442,12 +1473,12 @@ png_do_read_transformations(png_structp png_ptr)
           png_ptr->gamma_shift);
 #endif
 
-#if defined(PNG_READ_16_TO_8_SUPPORTED)
+#ifdef PNG_READ_16_TO_8_SUPPORTED
    if (png_ptr->transformations & PNG_16_TO_8)
       png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED)
+#ifdef PNG_READ_DITHER_SUPPORTED
    if (png_ptr->transformations & PNG_DITHER)
    {
       png_do_dither((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
@@ -1457,61 +1488,61 @@ png_do_read_transformations(png_structp png_ptr)
    }
 #endif
 
-#if defined(PNG_READ_INVERT_SUPPORTED)
+#ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
       png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_SHIFT_SUPPORTED)
+#ifdef PNG_READ_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
       png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
          &(png_ptr->shift));
 #endif
 
-#if defined(PNG_READ_PACK_SUPPORTED)
+#ifdef PNG_READ_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
       png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_BGR_SUPPORTED)
+#ifdef PNG_READ_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
       png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_PACKSWAP_SUPPORTED)
+#ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
       png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if we did not do so above */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
       png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_FILLER_SUPPORTED)
+#ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
       png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
          (png_uint_32)png_ptr->filler, png_ptr->flags);
 #endif
 
-#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
       png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED)
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
       png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_SWAP_SUPPORTED)
+#ifdef PNG_READ_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
       png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
     {
       if (png_ptr->read_user_transform_fn != NULL)
@@ -1525,7 +1556,7 @@ png_do_read_transformations(png_structp png_ptr)
                /*  png_byte channels;       number of channels (1-4) */
                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
                png_ptr->row_buf + 1);    /* start of pixel data for row */
-#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
+#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
       if (png_ptr->user_transform_depth)
          png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
       if (png_ptr->user_transform_channels)
@@ -1540,7 +1571,7 @@ png_do_read_transformations(png_structp png_ptr)
 
 }
 
-#if defined(PNG_READ_PACK_SUPPORTED)
+#ifdef PNG_READ_PACK_SUPPORTED
 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
  * without changing the actual values.  Thus, if you had a row with
  * a bit depth of 1, you would end up with bytes that only contained
@@ -1551,7 +1582,8 @@ void /* PRIVATE */
 png_do_unpack(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_unpack");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL && row_info->bit_depth < 8)
 #else
    if (row_info->bit_depth < 8)
@@ -1633,7 +1665,7 @@ png_do_unpack(png_row_infop row_info, png_bytep row)
 }
 #endif
 
-#if defined(PNG_READ_SHIFT_SUPPORTED)
+#ifdef PNG_READ_SHIFT_SUPPORTED
 /* Reverse the effects of png_do_shift.  This routine merely shifts the
  * pixels back to their significant bits values.  Thus, if you have
  * a row of bit depth 8, but only 5 are significant, this will shift
@@ -1643,8 +1675,9 @@ void /* PRIVATE */
 png_do_unshift(png_row_infop row_info, png_bytep row, png_color_8p sig_bits)
 {
    png_debug(1, "in png_do_unshift");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL && sig_bits != NULL &&
 #endif
        row_info->color_type != PNG_COLOR_TYPE_PALETTE)
@@ -1746,13 +1779,14 @@ png_do_unshift(png_row_infop row_info, png_bytep row, png_color_8p sig_bits)
 }
 #endif
 
-#if defined(PNG_READ_16_TO_8_SUPPORTED)
+#ifdef PNG_READ_16_TO_8_SUPPORTED
 /* Chop rows of bit depth 16 down to 8 */
 void /* PRIVATE */
 png_do_chop(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_chop");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL && row_info->bit_depth == 16)
 #else
    if (row_info->bit_depth == 16)
@@ -1765,7 +1799,7 @@ png_do_chop(png_row_infop row_info, png_bytep row)
 
       for (i = 0; i<istop; i++, sp += 2, dp++)
       {
-#if defined(PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED)
+#ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
       /* This does a more accurate scaling of the 16-bit color
        * value, rather than a simple low-byte truncation.
        *
@@ -1804,12 +1838,13 @@ png_do_chop(png_row_infop row_info, png_bytep row)
 }
 #endif
 
-#if defined(PNG_READ_SWAP_ALPHA_SUPPORTED)
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_read_swap_alpha");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL)
 #endif
    {
@@ -1896,12 +1931,13 @@ png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
 }
 #endif
 
-#if defined(PNG_READ_INVERT_ALPHA_SUPPORTED)
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_read_invert_alpha");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL)
 #endif
    {
@@ -1994,7 +2030,7 @@ png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
 }
 #endif
 
-#if defined(PNG_READ_FILLER_SUPPORTED)
+#ifdef PNG_READ_FILLER_SUPPORTED
 /* Add filler channel if we have RGB color */
 void /* PRIVATE */
 png_do_read_filler(png_row_infop row_info, png_bytep row,
@@ -2007,8 +2043,9 @@ png_do_read_filler(png_row_infop row_info, png_bytep row,
    png_byte lo_filler = (png_byte)(filler & 0xff);
 
    png_debug(1, "in png_do_read_filler");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL  && row_info != NULL &&
 #endif
        row_info->color_type == PNG_COLOR_TYPE_GRAY)
@@ -2170,7 +2207,7 @@ png_do_read_filler(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 /* Expand grayscale files to RGB, with or without alpha */
 void /* PRIVATE */
 png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
@@ -2179,8 +2216,9 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
    png_uint_32 row_width = row_info->width;
 
    png_debug(1, "in png_do_gray_to_rgb");
+
    if (row_info->bit_depth >= 8 &&
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
       !(row_info->color_type & PNG_COLOR_MASK_COLOR))
@@ -2253,7 +2291,7 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
 }
 #endif
 
-#if defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 /* Reduce RGB files to grayscale, with or without alpha
  * using the equation given in Poynton's ColorFAQ at
  * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008)
@@ -2285,8 +2323,9 @@ png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
    int rgb_error = 0;
 
    png_debug(1, "in png_do_rgb_to_gray");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
       (row_info->color_type & PNG_COLOR_MASK_COLOR))
@@ -2363,7 +2402,8 @@ png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
                   {
                      png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
                                   png_ptr->gamma_shift][red>>8];
-                     png_uint_16 green_1 = png_ptr->gamma_16_to_1[(green&0xff) >>
+                     png_uint_16 green_1 =
+                         png_ptr->gamma_16_to_1[(green&0xff) >>
                                   png_ptr->gamma_shift][green>>8];
                      png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
                                   png_ptr->gamma_shift][blue>>8];
@@ -2459,13 +2499,14 @@ png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
                   else
                   {
                      png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
-                                  png_ptr->gamma_shift][red>>8];
-                     png_uint_16 green_1 = png_ptr->gamma_16_to_1[(green&0xff) >>
-                                  png_ptr->gamma_shift][green>>8];
+                         png_ptr->gamma_shift][red>>8];
+                     png_uint_16 green_1 =
+                         png_ptr->gamma_16_to_1[(green&0xff) >>
+                         png_ptr->gamma_shift][green>>8];
                      png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
-                                  png_ptr->gamma_shift][blue>>8];
+                         png_ptr->gamma_shift][blue>>8];
                      png_uint_16 gray16  = (png_uint_16)((rc * red_1
-                                  + gc * green_1 + bc * blue_1)>>15);
+                         + gc * green_1 + bc * blue_1)>>15);
                      w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
                          png_ptr->gamma_shift][gray16 >> 8];
                      rgb_error |= 1;
@@ -2523,6 +2564,7 @@ png_build_grayscale_palette(int bit_depth, png_colorp palette)
    int v;
 
    png_debug(1, "in png_do_build_grayscale_palette");
+
    if (palette == NULL)
       return;
 
@@ -2563,14 +2605,17 @@ png_build_grayscale_palette(int bit_depth, png_colorp palette)
 }
 
 /* This function is currently unused.  Do we really need it? */
-#if defined(PNG_READ_DITHER_SUPPORTED) && defined(PNG_CORRECT_PALETTE_SUPPORTED)
+#if defined(PNG_READ_DITHER_SUPPORTED) && \
+  defined(PNG_CORRECT_PALETTE_SUPPORTED)
 void /* PRIVATE */
 png_correct_palette(png_structp png_ptr, png_colorp palette,
    int num_palette)
 {
    png_debug(1, "in png_correct_palette");
+
 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
-    defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
+    defined(PNG_READ_GAMMA_SUPPORTED) && \
+  defined(PNG_FLOATING_POINT_SUPPORTED)
    if (png_ptr->transformations & (PNG_GAMMA | PNG_BACKGROUND))
    {
       png_color back, back_1;
@@ -2591,8 +2636,8 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
 
          g = 1.0 / (png_ptr->background_gamma * png_ptr->screen_gamma);
 
-         if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_SCREEN ||
-             fabs(g - 1.0) < PNG_GAMMA_THRESHOLD)
+         if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_SCREEN
+             || fabs(g - 1.0) < PNG_GAMMA_THRESHOLD)
          {
             back.red = png_ptr->background.red;
             back.green = png_ptr->background.green;
@@ -2679,7 +2724,7 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
    }
    else
 #endif
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
    if (png_ptr->transformations & PNG_GAMMA)
    {
       int i;
@@ -2691,11 +2736,11 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
          palette[i].blue = png_ptr->gamma_table[palette[i].blue];
       }
    }
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    else
 #endif
 #endif
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
    if (png_ptr->transformations & PNG_BACKGROUND)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
@@ -2744,7 +2789,7 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
 }
 #endif
 
-#if defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
 /* Replace any alpha or transparency with the supplied background color.
  * "background" is already in the screen gamma, while "background_1" is
  * at a gamma of 1.0.  Paletted files have already been taken care of.
@@ -2752,7 +2797,7 @@ png_correct_palette(png_structp png_ptr, png_colorp palette,
 void /* PRIVATE */
 png_do_background(png_row_infop row_info, png_bytep row,
    png_color_16p trans_values, png_color_16p background
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
    , png_color_16p background_1,
    png_bytep gamma_table, png_bytep gamma_from_1, png_bytep gamma_to_1,
    png_uint_16pp gamma_16, png_uint_16pp gamma_16_from_1,
@@ -2766,8 +2811,9 @@ png_do_background(png_row_infop row_info, png_bytep row,
    int shift;
 
    png_debug(1, "in png_do_background");
+
    if (background != NULL &&
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
       (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
@@ -2804,7 +2850,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
 
                case 2:
                {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
@@ -2861,7 +2907,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
 
                case 4:
                {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
@@ -2918,7 +2964,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
 
                case 8:
                {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
                   {
                      sp = row;
@@ -2951,7 +2997,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
 
                case 16:
                {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_16 != NULL)
                   {
                      sp = row;
@@ -3000,7 +3046,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
          {
             if (row_info->bit_depth == 8)
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_table != NULL)
                {
                   sp = row;
@@ -3041,7 +3087,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
             }
             else /* if (row_info->bit_depth == 16) */
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL)
                {
                   sp = row;
@@ -3105,7 +3151,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
          {
             if (row_info->bit_depth == 8)
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
@@ -3147,7 +3193,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
                      {
                         *dp = *sp;
                      }
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else if (a == 0)
                      {
                         *dp = (png_byte)background->gray;
@@ -3164,7 +3210,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
             }
             else /* if (png_ptr->bit_depth == 16) */
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
                {
@@ -3182,7 +3228,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
                         *dp = (png_byte)((v >> 8) & 0xff);
                         *(dp + 1) = (png_byte)(v & 0xff);
                      }
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else if (a == 0)
 #else
                      else
@@ -3192,7 +3238,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
                         *dp = (png_byte)((background->gray >> 8) & 0xff);
                         *(dp + 1) = (png_byte)(background->gray & 0xff);
                      }
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else
                      {
                         png_uint_16 g, v, w;
@@ -3218,7 +3264,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
                      {
                         png_memcpy(dp, sp, 2);
                      }
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else if (a == 0)
 #else
                      else
@@ -3227,7 +3273,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
                         *dp = (png_byte)((background->gray >> 8) & 0xff);
                         *(dp + 1) = (png_byte)(background->gray & 0xff);
                      }
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                      else
                      {
                         png_uint_16 g, v;
@@ -3248,7 +3294,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
          {
             if (row_info->bit_depth == 8)
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
                {
@@ -3321,7 +3367,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
             }
             else /* if (row_info->bit_depth == 16) */
             {
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
                {
@@ -3438,7 +3484,7 @@ png_do_background(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
 /* Gamma correct the image, avoiding the alpha channel.  Make sure
  * you do this after you deal with the transparency issue on grayscale
  * or RGB images. If your bit depth is 8, use gamma_table, if it
@@ -3455,8 +3501,9 @@ png_do_gamma(png_row_infop row_info, png_bytep row,
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_gamma");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
        ((row_info->bit_depth <= 8 && gamma_table != NULL) ||
@@ -3579,10 +3626,10 @@ png_do_gamma(png_row_infop row_info, png_bytep row,
                   int d = *sp & 0x03;
 
                   *sp = (png_byte)(
-                        ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
-                        ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
-                        ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
-                        ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
+                      ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
+                      ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
+                      ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
+                      ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
                   sp++;
                }
             }
@@ -3596,7 +3643,7 @@ png_do_gamma(png_row_infop row_info, png_bytep row,
                   int lsb = *sp & 0x0f;
 
                   *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
-                          | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
+                      | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
                   sp++;
                }
             }
@@ -3629,7 +3676,7 @@ png_do_gamma(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#if defined(PNG_READ_EXPAND_SUPPORTED)
+#ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expands a palette row to an RGB or RGBA row depending
  * upon whether you supply trans and num_trans.
  */
@@ -3643,8 +3690,9 @@ png_do_expand_palette(png_row_infop row_info, png_bytep row,
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_expand_palette");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
        row_info->color_type == PNG_COLOR_TYPE_PALETTE)
@@ -3789,7 +3837,8 @@ png_do_expand(png_row_infop row_info, png_bytep row,
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_expand");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL)
 #endif
    {
@@ -3990,7 +4039,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED)
+#ifdef PNG_READ_DITHER_SUPPORTED
 void /* PRIVATE */
 png_do_dither(png_row_infop row_info, png_bytep row,
     png_bytep palette_lookup, png_bytep dither_lookup)
@@ -4000,7 +4049,8 @@ png_do_dither(png_row_infop row_info, png_bytep row,
    png_uint_32 row_width=row_info->width;
 
    png_debug(1, "in png_do_dither");
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+
+#ifdef PNG_USELESS_TESTS_SUPPORTED
    if (row != NULL && row_info != NULL)
 #endif
    {
@@ -4082,7 +4132,7 @@ png_do_dither(png_row_infop row_info, png_bytep row,
 #endif
 
 #ifdef PNG_FLOATING_POINT_SUPPORTED
-#if defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
 static PNG_CONST int png_gamma_shift[] =
    {0x10, 0x21, 0x42, 0x84, 0x110, 0x248, 0x550, 0xff0, 0x00};
 
@@ -4090,7 +4140,35 @@ static PNG_CONST int png_gamma_shift[] =
  * tables, we don't make a full table if we are reducing to 8-bit in
  * the future.  Note also how the gamma_16 tables are segmented so that
  * we don't need to allocate > 64K chunks for a full 16-bit table.
+ *
+ * See the PNG extensions document for an integer algorithm for creating
+ * the gamma tables.  Maybe we will implement that here someday.
+ *
+ * We should only reach this point if
+ *
+ *      the file_gamma is known (i.e., the gAMA or sRGB chunk is present,
+ *      or the application has provided a file_gamma)
+ *
+ *   AND
+ *      {
+ *         the screen_gamma is known
+ *      OR
+ *
+ *         RGB_to_gray transformation is being performed
+ *      }
+ *
+ *   AND
+ *      {
+ *         the screen_gamma is different from the reciprocal of the
+ *         file_gamma by more than the specified threshold
+ *
+ *      OR
+ *
+ *         a background color has been specified and the file_gamma
+ *         and screen_gamma are not 1.0, within the specified threshold.
+ *      }
  */
+
 void /* PRIVATE */
 png_build_gamma_table(png_structp png_ptr)
 {
@@ -4200,9 +4278,8 @@ png_build_gamma_table(png_structp png_ptr)
      else
         g = 1.0;
 
-     png_ptr->gamma_16_table = (png_uint_16pp)png_malloc(png_ptr,
+     png_ptr->gamma_16_table = (png_uint_16pp)png_calloc(png_ptr,
         (png_uint_32)(num * png_sizeof(png_uint_16p)));
-     png_memset(png_ptr->gamma_16_table, 0, num * png_sizeof(png_uint_16p)); 
 
      if (png_ptr->transformations & (PNG_16_TO_8 | PNG_BACKGROUND))
      {
@@ -4262,9 +4339,8 @@ png_build_gamma_table(png_structp png_ptr)
 
         g = 1.0 / (png_ptr->gamma);
 
-        png_ptr->gamma_16_to_1 = (png_uint_16pp)png_malloc(png_ptr,
+        png_ptr->gamma_16_to_1 = (png_uint_16pp)png_calloc(png_ptr,
            (png_uint_32)(num * png_sizeof(png_uint_16p )));
-        png_memset(png_ptr->gamma_16_to_1, 0, num * png_sizeof(png_uint_16p)); 
 
         for (i = 0; i < num; i++)
         {
@@ -4287,10 +4363,8 @@ png_build_gamma_table(png_structp png_ptr)
         else
            g = png_ptr->gamma;   /* Probably doing rgb_to_gray */
 
-        png_ptr->gamma_16_from_1 = (png_uint_16pp)png_malloc(png_ptr,
+        png_ptr->gamma_16_from_1 = (png_uint_16pp)png_calloc(png_ptr,
            (png_uint_32)(num * png_sizeof(png_uint_16p)));
-        png_memset(png_ptr->gamma_16_from_1, 0,
-           num * png_sizeof(png_uint_16p)); 
 
         for (i = 0; i < num; i++)
         {
@@ -4315,14 +4389,15 @@ png_build_gamma_table(png_structp png_ptr)
 /* To do: install integer version of png_build_gamma_table here */
 #endif
 
-#if defined(PNG_MNG_FEATURES_SUPPORTED)
+#ifdef PNG_MNG_FEATURES_SUPPORTED
 /* Undoes intrapixel differencing  */
 void /* PRIVATE */
 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
 {
    png_debug(1, "in png_do_read_intrapixel");
+
    if (
-#if defined(PNG_USELESS_TESTS_SUPPORTED)
+#ifdef PNG_USELESS_TESTS_SUPPORTED
        row != NULL && row_info != NULL &&
 #endif
        (row_info->color_type & PNG_COLOR_MASK_COLOR))