// 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 <string>
#include <vector>
#include "base/basictypes.h"
#include "ui/gfx/gfx_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 GFX_EXPORT 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,
// SkBitmap format. For Encode() kARGB_8888_Config (4 bytes per pixel) and
// kA8_Config (1 byte per pixel) formats are supported. kA8_Config gets
// encoded into a grayscale PNG treating alpha as the color intensity.
// For Decode() kARGB_8888_Config is always used.
FORMAT_SkBitmap
};
// Represents a comment in the tEXt ancillary chunk of the png.
struct GFX_EXPORT Comment {
Comment(const std::string& k, const std::string& t);
~Comment();
std::string key;
std::string text;
};
// 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 kARGB_8888_Config, 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);
// 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 kA8_Config, 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. During the call,
// an SkAutoLockPixels lock is held on |input|.
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);
private:
DISALLOW_COPY_AND_ASSIGN(PNGCodec);
};
} // namespace gfx
#endif // UI_GFX_CODEC_PNG_CODEC_H_