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- // 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_
- #include <stddef.h>
- #include <string>
- #include <vector>
- #include "ui/gfx/codec/codec_export.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 CODEC_EXPORT PNGCodec {
- public:
- static constexpr int DEFAULT_ZLIB_COMPRESSION = 6;
- enum ColorFormat {
- // 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,
- // SkBitmap format. For Encode() kN32_SkColorType (4 bytes per pixel) and
- // kAlpha_8_SkColorType (1 byte per pixel) formats are supported.
- // kAlpha_8_SkColorType gets encoded into a grayscale PNG treating alpha as
- // the color intensity. For Decode() kN32_SkColorType is always used.
- FORMAT_SkBitmap
- };
- // Represents a comment in the tEXt ancillary chunk of the png.
- struct CODEC_EXPORT Comment {
- Comment(const std::string& k, const std::string& t);
- ~Comment();
- std::string key;
- std::string text;
- };
- PNGCodec(const PNGCodec&) = delete;
- PNGCodec& operator=(const PNGCodec&) = delete;
- // 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.
- //
- // 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.
- // 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 kN32_SkColorType, 32 bits per pixel. The params |discard_transparency|
- // and |output| are passed directly to Encode; refer to Encode for more
- // information.
- static bool EncodeBGRASkBitmap(const SkBitmap& input,
- bool discard_transparency,
- std::vector<unsigned char>* output);
- // Call PNGCodec::Encode on the supplied SkBitmap |input|. The difference
- // between this and the previous method is that this restricts compression to
- // zlib q1, which is just rle encoding.
- static bool FastEncodeBGRASkBitmap(const SkBitmap& input,
- bool discard_transparency,
- std::vector<unsigned char>* output);
- // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed to
- // be kAlpha_8_SkColorType, 8 bits per pixel. The bitmap is encoded as a
- // grayscale PNG with alpha used for color intensity. The |output| param is
- // passed directly to Encode; refer to Encode for more information.
- static bool EncodeA8SkBitmap(const SkBitmap& input,
- std::vector<unsigned char>* output);
- // Decodes the PNG data contained in input of length input_size. The
- // decoded data will be placed in *output with the dimensions in *w and *h
- // on success (returns true). This data will be written in the 'format'
- // format. On failure, the values of these output variables are undefined.
- //
- // This function may not support all PNG types, and it hasn't been tested
- // with a large number of images, so assume a new format may not work. It's
- // really designed to be able to read in something written by Encode() above.
- static bool Decode(const unsigned char* input, size_t input_size,
- ColorFormat format, std::vector<unsigned char>* output,
- int* w, int* h);
- // Decodes the PNG data directly into the passed in SkBitmap. This is
- // significantly faster than the vector<unsigned char> version of Decode()
- // above when dealing with PNG files that are >500K, which a lot of theme
- // images are. (There are a lot of themes that have a NTP image of about ~1
- // megabyte, and those require a 7-10 megabyte side buffer.)
- //
- // Returns true if data is non-null and can be decoded as a png, false
- // otherwise.
- static bool Decode(const unsigned char* input, size_t input_size,
- SkBitmap* bitmap);
- };
- } // namespace gfx
- #endif // UI_GFX_CODEC_PNG_CODEC_H_
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