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
14class SkBitmap;
15
16namespace gfx {
17
18class 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.
26class 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_
135