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/gfx/gfx_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 GFX_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     // SkBitmap format. For Encode() kARGB_8888_Config (4 bytes per pixel) and
  41     // kA8_Config (1 byte per pixel) formats are supported. kA8_Config gets
  42     // encoded into a grayscale PNG treating alpha as the color intensity.
  43     // For Decode() kARGB_8888_Config is always used.
  44     FORMAT_SkBitmap
  45   };
  46
  47   // Represents a comment in the tEXt ancillary chunk of the png.
  48   struct GFX_EXPORT Comment {
  49     Comment(const std::string& k, const std::string& t);
  50     ~Comment();
  51
  52     std::string key;
  53     std::string text;
  54   };
  55
  56   // Encodes the given raw 'input' data, with each pixel being represented as
  57   // given in 'format'. The encoded PNG data will be written into the supplied
  58   // vector and true will be returned on success. On failure (false), the
  59   // contents of the output buffer are undefined.
  60   //
  61   // When writing alpha values, the input colors are assumed to be post
  62   // multiplied.
  63   //
  64   // size: dimensions of the image
  65   // row_byte_width: the width in bytes of each row. This may be greater than
  66   //   w * bytes_per_pixel if there is extra padding at the end of each row
  67   //   (often, each row is padded to the next machine word).
  68   // discard_transparency: when true, and when the input data format includes
  69   //   alpha values, these alpha values will be discarded and only RGB will be
  70   //   written to the resulting file. Otherwise, alpha values in the input
  71   //   will be preserved.
  72   // comments: comments to be written in the png's metadata.
  73   static bool Encode(const unsigned char* input,
  74                      ColorFormat format,
  75                      const Size& size,
  76                      int row_byte_width,
  77                      bool discard_transparency,
  78                      const std::vector<Comment>& comments,
  79                      std::vector<unsigned char>* output);
  80
  81   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
  82   // to be kARGB_8888_Config, 32 bits per pixel. The params
  83   // |discard_transparency| and |output| are passed directly to Encode; refer to
  84   // Encode for more information. During the call, an SkAutoLockPixels lock
  85   // is held on |input|.
  86   static bool EncodeBGRASkBitmap(const SkBitmap& input,
  87                                  bool discard_transparency,
  88                                  std::vector<unsigned char>* output);
  89
  90   // Call PNGCodec::Encode on the supplied SkBitmap |input|. The difference
  91   // between this and the previous method is that this restricts compression to
  92   // zlib q1, which is just rle encoding.
  93   static bool FastEncodeBGRASkBitmap(const SkBitmap& input,
  94                                      bool discard_transparency,
  95                                      std::vector<unsigned char>* output);
  96
  97   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
  98   // to be kA8_Config, 8 bits per pixel. The bitmap is encoded as a grayscale
  99   // PNG with alpha used for color intensity. The |output| param is passed
 100   // directly to Encode; refer to Encode for more information. During the call,
 101   // an SkAutoLockPixels lock is held on |input|.
 102   static bool EncodeA8SkBitmap(const SkBitmap& input,
 103                                std::vector<unsigned char>* output);
 104
 105   // Decodes the PNG data contained in input of length input_size. The
 106   // decoded data will be placed in *output with the dimensions in *w and *h
 107   // on success (returns true). This data will be written in the 'format'
 108   // format. On failure, the values of these output variables are undefined.
 109   //
 110   // This function may not support all PNG types, and it hasn't been tested
 111   // with a large number of images, so assume a new format may not work. It's
 112   // really designed to be able to read in something written by Encode() above.
 113   static bool Decode(const unsigned char* input, size_t input_size,
 114                      ColorFormat format, std::vector<unsigned char>* output,
 115                      int* w, int* h);
 116
 117   // Decodes the PNG data directly into the passed in SkBitmap. This is
 118   // significantly faster than the vector<unsigned char> version of Decode()
 119   // above when dealing with PNG files that are >500K, which a lot of theme
 120   // images are. (There are a lot of themes that have a NTP image of about ~1
 121   // megabyte, and those require a 7-10 megabyte side buffer.)
 122   //
 123   // Returns true if data is non-null and can be decoded as a png, false
 124   // otherwise.
 125   static bool Decode(const unsigned char* input, size_t input_size,
 126                      SkBitmap* bitmap);
 127
 128  private:
 129   DISALLOW_COPY_AND_ASSIGN(PNGCodec);
 130 };
 131
 132 }  // namespace gfx
 133
 134 #endif  // UI_GFX_CODEC_PNG_CODEC_H_