ui/gfx/codec/png_codec.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_GFX_CODEC_PNG_CODEC_H_
   6 #define UI_GFX_CODEC_PNG_CODEC_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "ui/base/ui_export.h"
  13
  14 class SkBitmap;
  15
  16 namespace gfx {
  17
  18 class Size;
  19
  20 // Interface for encoding and decoding PNG data. This is a wrapper around
  21 // libpng, which has an inconvenient interface for callers. This is currently
  22 // designed for use in tests only (where we control the files), so the handling
  23 // isn't as robust as would be required for a browser (see Decode() for more).
  24 // WebKit has its own more complicated PNG decoder which handles, among other
  25 // things, partially downloaded data.
  26 class UI_EXPORT PNGCodec {
  27  public:
  28   enum ColorFormat {
  29     // 3 bytes per pixel (packed), in RGB order regardless of endianness.
  30     // This is the native JPEG format.
  31     FORMAT_RGB,
  32
  33     // 4 bytes per pixel, in RGBA order in memory regardless of endianness.
  34     FORMAT_RGBA,
  35
  36     // 4 bytes per pixel, in BGRA order in memory regardless of endianness.
  37     // This is the default Windows DIB order.
  38     FORMAT_BGRA,
  39
  40     // 4 bytes per pixel, in pre-multiplied kARGB_8888_Config format. For use
  41     // with directly writing to a skia bitmap.
  42     FORMAT_SkBitmap
  43   };
  44
  45   // Represents a comment in the tEXt ancillary chunk of the png.
  46   struct UI_EXPORT Comment {
  47     Comment(const std::string& k, const std::string& t);
  48     ~Comment();
  49
  50     std::string key;
  51     std::string text;
  52   };
  53
  54   // Calls PNGCodec::EncodeWithCompressionLevel with the default compression
  55   // level.
  56   static bool Encode(const unsigned char* input,
  57                      ColorFormat format,
  58                      const Size& size,
  59                      int row_byte_width,
  60                      bool discard_transparency,
  61                      const std::vector<Comment>& comments,
  62                      std::vector<unsigned char>* output);
  63
  64   // Encodes the given raw 'input' data, with each pixel being represented as
  65   // given in 'format'. The encoded PNG data will be written into the supplied
  66   // vector and true will be returned on success. On failure (false), the
  67   // contents of the output buffer are undefined.
  68   //
  69   // When writing alpha values, the input colors are assumed to be post
  70   // multiplied.
  71   //
  72   // size: dimensions of the image
  73   // row_byte_width: the width in bytes of each row. This may be greater than
  74   //   w * bytes_per_pixel if there is extra padding at the end of each row
  75   //   (often, each row is padded to the next machine word).
  76   // discard_transparency: when true, and when the input data format includes
  77   //   alpha values, these alpha values will be discarded and only RGB will be
  78   //   written to the resulting file. Otherwise, alpha values in the input
  79   //   will be preserved.
  80   // comments: comments to be written in the png's metadata.
  81   // compression_level: An integer between -1 and 9, corresponding to zlib's
  82   //   compression levels. -1 is the default.
  83   static bool EncodeWithCompressionLevel(const unsigned char* input,
  84                                          ColorFormat format,
  85                                          const Size& size,
  86                                          int row_byte_width,
  87                                          bool discard_transparency,
  88                                          const std::vector<Comment>& comments,
  89                                          int compression_level,
  90                                          std::vector<unsigned char>* output);
  91
  92   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
  93   // to be BGRA, 32 bits per pixel. The params |discard_transparency| and
  94   // |output| are passed directly to Encode; refer to Encode for more
  95   // information. During the call, an SkAutoLockPixels lock is held on |input|.
  96   static bool EncodeBGRASkBitmap(const SkBitmap& input,
  97                                  bool discard_transparency,
  98                                  std::vector<unsigned char>* output);
  99
 100   // Decodes the PNG data contained in input of length input_size. The
 101   // decoded data will be placed in *output with the dimensions in *w and *h
 102   // on success (returns true). This data will be written in the 'format'
 103   // format. On failure, the values of these output variables are undefined.
 104   //
 105   // This function may not support all PNG types, and it hasn't been tested
 106   // with a large number of images, so assume a new format may not work. It's
 107   // really designed to be able to read in something written by Encode() above.
 108   static bool Decode(const unsigned char* input, size_t input_size,
 109                      ColorFormat format, std::vector<unsigned char>* output,
 110                      int* w, int* h);
 111
 112   // Decodes the PNG data directly into the passed in SkBitmap. This is
 113   // significantly faster than the vector<unsigned char> version of Decode()
 114   // above when dealing with PNG files that are >500K, which a lot of theme
 115   // images are. (There are a lot of themes that have a NTP image of about ~1
 116   // megabyte, and those require a 7-10 megabyte side buffer.)
 117   //
 118   // Returns true if data is non-null and can be decoded as a png, false
 119   // otherwise.
 120   static bool Decode(const unsigned char* input, size_t input_size,
 121                      SkBitmap* bitmap);
 122
 123   // Create a SkBitmap from a decoded BGRA DIB. The caller owns the returned
 124   // SkBitmap.
 125   static SkBitmap* CreateSkBitmapFromBGRAFormat(
 126       std::vector<unsigned char>& bgra, int width, int height);
 127
 128  private:
 129   DISALLOW_COPY_AND_ASSIGN(PNGCodec);
 130 };
 131
 132 }  // namespace gfx
 133
 134 #endif  // UI_GFX_CODEC_PNG_CODEC_H_