Add the ability to write comments to PNGCodec::Encode.

ui/gfx/codec/png_codec.cc

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/codec/png_codec.h"
 
 #include "base/logging.h"
 #include "base/scoped_ptr.h"
+#include "ui/gfx/size.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkUnPreMultiply.h"
 #include "third_party/skia/include/core/SkColorPriv.h"
 
 extern "C" {
 #if defined(USE_SYSTEM_LIBPNG)
 #include <png.h>
 #else
 #include "third_party/libpng/png.h"
 #endif
@@ skipping 520 matching lines @@
                       unsigned char* rgb, bool* is_opaque) {
   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];
   }
 }
 
+#ifdef PNG_TEXT_SUPPORTED
+class CommentWriter {
+ public:
+  explicit CommentWriter(const std::vector<PNGCodec::Comment>& comments)
+      : comments_(comments), png_text_(new png_text[comments.size()]) {

[brettw, 2011/03/25 00:06:09]

Style guide implies these should go on different lines (exception is when
absolutely everything fits on one line).

[tony, 2011/03/25 01:04:44]

Done.

+    for (size_t i = 0; i < comments.size(); ++i)
+      AddComment(i, comments[i]);
+  }
+
+  ~CommentWriter() {
+    for (size_t i = 0; i < comments_.size(); ++i) {
+      free(png_text_[i].key);
+      free(png_text_[i].text);
+    }
+    delete [] png_text_;
+  }
+
+  bool HasComments() {
+    return !comments_.empty();
+  }
+
+  png_text* get_png_text() {
+    return png_text_;
+  }
+
+  int size() {
+    return static_cast<int>(comments_.size());
+  }
+
+ private:
+  void AddComment(size_t pos, const PNGCodec::Comment& comment) {
+    png_text_[pos].compression = PNG_TEXT_COMPRESSION_NONE;
+    // A PNG comment's can only be 79 characters long.

[brettw, 2011/03/25 00:06:09]

Maybe a DCHECK on the length here would be nice so people aren't shocked if
their comments get truncated.

[tony, 2011/03/25 01:04:44]

Done.

+    png_text_[pos].key = strdup(comment.key.substr(0, 78).c_str());
+    png_text_[pos].text = strdup(comment.text.c_str());
+    png_text_[pos].text_length = comment.text.length();
+#ifdef PNG_iTXt_SUPPORTED
+    png_text_[pos].itxt_length = 0;
+    png_text_[pos].lang = 0;
+    png_text_[pos].lang_key = 0;
+#endif
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(CommentWriter);
+
+  const std::vector<PNGCodec::Comment> comments_;
+  png_text* png_text_;
+};
+#endif  // PNG_TEXT_SUPPORTED
+
 // The type of functions usable for converting between pixel formats.
 typedef void (*FormatConverter)(const unsigned char* in, int w,
                                 unsigned char* out, bool* is_opaque);
 
 // libpng uses a wacky setjmp-based API, which makes the compiler nervous.
 // We constrain all of the calls we make to libpng where the setjmp() is in
 // place to this function.
 // Returns true on success.
 bool DoLibpngWrite(png_struct* png_ptr, png_info* info_ptr,
                    PngEncoderState* state,
                    int width, int height, int row_byte_width,
                    const unsigned char* input,
                    int png_output_color_type, int output_color_components,
-                   FormatConverter converter) {
+                   FormatConverter converter,
+                   const std::vector<PNGCodec::Comment>& comments) {
   // Make sure to not declare any locals here -- locals in the presence
   // of setjmp() in C++ code makes gcc complain.
 
   if (setjmp(png_jmpbuf(png_ptr)))
     return false;
 
   // Set our callback for libpng to give us the data.
   png_set_write_fn(png_ptr, state, EncoderWriteCallback, FakeFlushCallback);
 
   png_set_IHDR(png_ptr, info_ptr, width, height, 8, png_output_color_type,
                PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
                PNG_FILTER_TYPE_DEFAULT);
+
+#ifdef PNG_TEXT_SUPPORTED
+  CommentWriter comment_writer(comments);
+  if (comment_writer.HasComments()) {
+    png_set_text(png_ptr, info_ptr, comment_writer.get_png_text(),
+                 comment_writer.size());
+  }
+#endif
+
   png_write_info(png_ptr, info_ptr);
 
   if (!converter) {
     // No conversion needed, give the data directly to libpng.
     for (int y = 0; y < height; 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[width * output_color_components];
     for (int y = 0; y < height; y ++) {
       converter(&input[y * row_byte_width], width, row, NULL);
       png_write_row(png_ptr, row);
     }
     delete[] row;
   }
 
   png_write_end(png_ptr, info_ptr);
   return true;
 }
 
 }  // namespace
 
 // static
 bool PNGCodec::Encode(const unsigned char* input, ColorFormat format,
-                      int w, int h, int row_byte_width,
+                      const Size& size, int row_byte_width,
                       bool discard_transparency,
+                      const std::vector<Comment>& comments,
                       std::vector<unsigned char>* output) {
   // Run to convert an input row into the output row format, NULL means no
   // conversion is necessary.
   FormatConverter converter = NULL;
 
   int input_color_components, output_color_components;
   int png_output_color_type;
   switch (format) {
     case FORMAT_RGB:
       input_color_components = 3;
@@ skipping 40 matching lines @@
         converter = ConvertSkiatoRGBA;
       }
       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);
+  DCHECK(input_color_components * size.width() <= row_byte_width);
 
   png_struct* png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
                                                 NULL, NULL, 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;
   }
 
   PngEncoderState state(output);
   bool success = DoLibpngWrite(png_ptr, info_ptr, &state,
-                               w, h, row_byte_width, input,
-                               png_output_color_type, output_color_components,
-                               converter);
+                               size.width(), size.height(), row_byte_width,
+                               input, png_output_color_type,
+                               output_color_components, converter, comments);
   png_destroy_write_struct(&png_ptr, &info_ptr);
 
   return success;
 }
 
 // static
 bool PNGCodec::EncodeBGRASkBitmap(const SkBitmap& input,
                                   bool discard_transparency,
                                   std::vector<unsigned char>* output) {
   static const int bbp = 4;
 
   SkAutoLockPixels lock_input(input);
   DCHECK(input.empty() || input.bytesPerPixel() == bbp);
 
   return Encode(reinterpret_cast<unsigned char*>(input.getAddr32(0, 0)),
-                FORMAT_SkBitmap, input.width(), input.height(),
-                input.width() * bbp, discard_transparency, output);
+                FORMAT_SkBitmap, Size(input.width(), input.height()),
+                input.width() * bbp, discard_transparency,
+                std::vector<Comment>(), output);
 }
 
 }  // namespace gfx