1 files changed, 217 insertions, 0 deletions
diff --git a/base/gfx/png_encoder.cc b/base/gfx/png_encoder.cc
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "base/basictypes.h"
+#include "base/gfx/png_encoder.h"
+#include "base/logging.h"
+
+extern "C" {
+#include "png.h"
+}
+
+namespace {
+
+// Converts BGRA->RGBA and RGBA->BGRA.
+void ConvertBetweenBGRAandRGBA(const unsigned char* input, int pixel_width,
+                               unsigned char* output) {
+  for (int x = 0; x < pixel_width; x++) {
+    const unsigned char* pixel_in = &input[x * 4];
+    unsigned char* pixel_out = &output[x * 4];
+    pixel_out[0] = pixel_in[2];
+    pixel_out[1] = pixel_in[1];
+    pixel_out[2] = pixel_in[0];
+    pixel_out[3] = pixel_in[3];
+  }
+}
+
+void ConvertRGBAtoRGB(const unsigned char* rgba, int pixel_width,
+                      unsigned char* rgb) {
+  for (int x = 0; x < pixel_width; x++) {
+    const unsigned char* pixel_in = &rgba[x * 4];
+    unsigned char* pixel_out = &rgb[x * 3];
+    pixel_out[0] = pixel_in[0];
+    pixel_out[1] = pixel_in[1];
+    pixel_out[2] = pixel_in[2];
+  }
+}
+
+}  // namespace
+
+// Encoder --------------------------------------------------------------------
+//
+// This section of the code is based on nsPNGEncoder.cpp in Mozilla
+// (Copyright 2005 Google Inc.)
+
+namespace {
+
+// Passed around as the io_ptr in the png structs so our callbacks know where
+// to write data.
+struct PngEncoderState {
+  PngEncoderState(std::vector<unsigned char>* o) : out(o) {}
+  std::vector<unsigned char>* out;
+};
+
+// Called by libpng to flush its internal buffer to ours.
+void EncoderWriteCallback(png_structp png, png_bytep data, png_size_t size) {
+  PngEncoderState* state = static_cast<PngEncoderState*>(png_get_io_ptr(png));
+  DCHECK(state->out);
+
+  size_t old_size = state->out->size();
+  state->out->resize(old_size + size);
+  memcpy(&(*state->out)[old_size], data, size);
+}
+
+void ConvertBGRAtoRGB(const unsigned char* bgra, int pixel_width,
+                      unsigned char* rgb) {
+  for (int x = 0; x < pixel_width; x++) {
+    const unsigned char* pixel_in = &bgra[x * 4];
+    unsigned char* pixel_out = &rgb[x * 3];
+    pixel_out[0] = pixel_in[2];
+    pixel_out[1] = pixel_in[1];
+    pixel_out[2] = pixel_in[0];
+  }
+}
+
+// Automatically destroys the given write structs on destruction to make
+// cleanup and error handling code cleaner.
+class PngWriteStructDestroyer {
+ public:
+  PngWriteStructDestroyer(png_struct** ps, png_info** pi) : ps_(ps), pi_(pi) {
+  }
+  ~PngWriteStructDestroyer() {
+    png_destroy_write_struct(ps_, pi_);
+  }
+ private:
+  png_struct** ps_;
+  png_info** pi_;
+
+  DISALLOW_EVIL_CONSTRUCTORS(PngWriteStructDestroyer);
+};
+
+}  // namespace
+
+// static
+bool PNGEncoder::Encode(const unsigned char* input, ColorFormat format,
+                      int w, int h, int row_byte_width,
+                      bool discard_transparency,
+                      std::vector<unsigned char>* output) {
+  // Run to convert an input row into the output row format, NULL means no
+  // conversion is necessary.
+  void (*converter)(const unsigned char* in, int w, unsigned char* out) = NULL;
+
+  int input_color_components, output_color_components;
+  int png_output_color_type;
+  switch (format) {
+    case FORMAT_RGB:
+      input_color_components = 3;
+      output_color_components = 3;
+      png_output_color_type = PNG_COLOR_TYPE_RGB;
+      discard_transparency = false;
+      break;
+
+    case FORMAT_RGBA:
+      input_color_components = 4;
+      if (discard_transparency) {
+        output_color_components = 3;
+        png_output_color_type = PNG_COLOR_TYPE_RGB;
+        converter = ConvertRGBAtoRGB;
+      } else {
+        output_color_components = 4;
+        png_output_color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+        converter = NULL;
+      }
+      break;
+
+    case FORMAT_BGRA:
+      input_color_components = 4;
+      if (discard_transparency) {
+        output_color_components = 3;
+        png_output_color_type = PNG_COLOR_TYPE_RGB;
+        converter = ConvertBGRAtoRGB;
+      } else {
+        output_color_components = 4;
+        png_output_color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+        converter = ConvertBetweenBGRAandRGBA;
+      }
+      break;
+
+    default:
+      NOTREACHED() << "Unknown pixel format";
+      return false;
+  }
+
+  // Row stride should be at least as long as the length of the data.
+  DCHECK(input_color_components * w <= row_byte_width);
+
+  png_struct* png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
+                                                png_voidp_NULL,
+                                                png_error_ptr_NULL,
+                                                png_error_ptr_NULL);
+  if (!png_ptr)
+    return false;
+  png_info* info_ptr = png_create_info_struct(png_ptr);
+  if (!info_ptr) {
+    png_destroy_write_struct(&png_ptr, NULL);
+    return false;
+  }
+  PngWriteStructDestroyer destroyer(&png_ptr, &info_ptr);
+
+  if (setjmp(png_jmpbuf(png_ptr))) {
+    // The destroyer will ensure that the structures are cleaned up in this
+    // case, even though we may get here as a jump from random parts of the
+    // PNG library called below.
+    return false;
+  }
+
+  // Set our callback for libpng to give us the data.
+  PngEncoderState state(output);
+  png_set_write_fn(png_ptr, &state, EncoderWriteCallback, NULL);
+
+  png_set_IHDR(png_ptr, info_ptr, w, h, 8, png_output_color_type,
+               PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
+               PNG_FILTER_TYPE_DEFAULT);
+  png_write_info(png_ptr, info_ptr);
+
+  if (!converter) {
+    // No conversion needed, give the data directly to libpng.
+    for (int y = 0; y < h; y ++)
+      png_write_row(png_ptr, const_cast<unsigned char*>(&input[y * row_byte_width]));
+  } else {
+    // Needs conversion using a separate buffer.
+    unsigned char* row = new unsigned char[w * output_color_components];
+    for (int y = 0; y < h; y ++) {
+      converter(&input[y * row_byte_width], w, row);
+      png_write_row(png_ptr, row);
+    }
+    delete[] row;
+  }
+
+  png_write_end(png_ptr, info_ptr);
+  return true;
+}