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

ui/gfx/codec/png_codec.h

-// Copyright (c) 2006-2008 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.
 
 #ifndef UI_GFX_CODEC_PNG_CODEC_H_
 #define UI_GFX_CODEC_PNG_CODEC_H_
 #pragma once
 
+#include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 
 class SkBitmap;
 
 namespace gfx {
 
+class Size;
+
 // Interface for encoding and decoding PNG data. This is a wrapper around
 // libpng, which has an inconvenient interface for callers. This is currently
 // designed for use in tests only (where we control the files), so the handling
 // isn't as robust as would be required for a browser (see Decode() for more).
 // WebKit has its own more complicated PNG decoder which handles, among other
 // things, partially downloaded data.
 class PNGCodec {
  public:
   enum ColorFormat {
     // 3 bytes per pixel (packed), in RGB order regardless of endianness.
     // This is the native JPEG format.
     FORMAT_RGB,
 
     // 4 bytes per pixel, in RGBA order in memory regardless of endianness.
     FORMAT_RGBA,
 
     // 4 bytes per pixel, in BGRA order in memory regardless of endianness.
     // This is the default Windows DIB order.
     FORMAT_BGRA,
 
     // 4 bytes per pixel, in pre-multiplied kARGB_8888_Config format. For use
     // with directly writing to a skia bitmap.
     FORMAT_SkBitmap
   };
 
+  // Represents a comment in the tEXt ancillary chunk of the png.
+  struct Comment {
+    std::string key;
+    std::string text;
+    Comment(const std::string& k, const std::string& t) : key(k), text(t) {}

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

Wouldn't this constructor normally go first?

Can you make this non-inline and also write a non-inline destructor so we don't
get this instantiated all over the place (channeling erg).

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

Done.

+  };
+
   // Encodes the given raw 'input' data, with each pixel being represented as
   // given in 'format'. The encoded PNG data will be written into the supplied
   // vector and true will be returned on success. On failure (false), the
   // contents of the output buffer are undefined.
   //
   // When writing alpha values, the input colors are assumed to be post
   // multiplied.
   //
-  // w, h: dimensions of the image
+  // size: dimensions of the image
   // row_byte_width: the width in bytes of each row. This may be greater than
   //   w * bytes_per_pixel if there is extra padding at the end of each row
   //   (often, each row is padded to the next machine word).
   // discard_transparency: when true, and when the input data format includes
   //   alpha values, these alpha values will be discarded and only RGB will be
   //   written to the resulting file. Otherwise, alpha values in the input
   //   will be preserved.
-  static bool Encode(const unsigned char* input, ColorFormat format,
-                     int w, int h, int row_byte_width,
+  // comments: comments to be written in the png's metadata.
+  static bool Encode(const unsigned char* input,
+                     ColorFormat format,
+                     const Size& size,
+                     int row_byte_width,
                      bool discard_transparency,
+                     const std::vector<Comment>& comments,
                      std::vector<unsigned char>* output);
 
   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
   // to be BGRA, 32 bits per pixel. The params |discard_transparency| and
   // |output| are passed directly to Encode; refer to Encode for more
   // information. During the call, an SkAutoLockPixels lock is held on |input|.
   static bool EncodeBGRASkBitmap(const SkBitmap& input,
                                  bool discard_transparency,
                                  std::vector<unsigned char>* output);
 
@@ skipping 25 matching lines @@
   static SkBitmap* CreateSkBitmapFromBGRAFormat(
       std::vector<unsigned char>& bgra, int width, int height);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PNGCodec);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_CODEC_PNG_CODEC_H_