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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
/*
* PNG decoder used in engines:
* - sword25
* Dependencies:
* - zlib
*/
#ifndef GRAPHICS_PNG_H
#define GRAPHICS_PNG_H
// PNG decoder, based on the W3C specs:
// http://www.w3.org/TR/PNG/
// Parts of the code have been adapted from LodePNG, by Lode Vandevenne:
// http://members.gamedev.net/lode/projects/LodePNG/
// All the numbers are BE: http://www.w3.org/TR/PNG/#7Integers-and-byte-order
// Note: At the moment, this decoder only supports non-interlaced images, and
// does not support truecolor/grayscale images with 16bit depth.
//
// Theoretically, interlaced images shouldn't be needed for games, as
// interlacing is only useful for images in websites.
//
// PNG images with 16bit depth (i.e. 48bit images) are quite rare, and can
// theoretically contain more than 16.7 millions of colors (the so-called "deep
// color" representation). In essence, each of the R, G, B and A components in
// them is specified with 2 bytes, instead of 1. However, the PNG specification
// always refers to color components with 1 byte each, so this part of the spec
// is a bit unclear. For now, these won't be supported, until a suitable sample
// is found.
#include "common/scummsys.h"
#include "common/textconsole.h"
#include "graphics/decoders/image_decoder.h"
namespace Common {
class SeekableReadStream;
}
namespace Graphics {
struct Surface;
struct PixelFormat;
class PNGDecoder : public ImageDecoder {
public:
PNGDecoder();
~PNGDecoder();
bool loadStream(Common::SeekableReadStream &stream);
void destroy();
const Graphics::Surface *getSurface() const { return _outputSurface; }
const byte *getPalette() const { return _palette; }
uint16 getPaletteColorCount() const { return _paletteEntries; }
private:
enum PNGColorType {
kGrayScale = 0, // bit depths: 1, 2, 4, 8, 16
kTrueColor = 2, // bit depths: 8, 16
kIndexed = 3, // bit depths: 1, 2, 4, 8
kGrayScaleWithAlpha = 4, // bit depths: 8, 16
kTrueColorWithAlpha = 6 // bit depths: 8, 16
};
enum PNGInterlaceType {
kNonInterlaced = 0,
kInterlaced = 1
};
struct PNGHeader {
uint32 width;
uint32 height;
byte bitDepth;
PNGColorType colorType;
byte compressionMethod;
byte filterMethod;
PNGInterlaceType interlaceType;
};
void readHeaderChunk();
byte getNumColorChannels() const;
void readPaletteChunk();
void readTransparencyChunk(uint32 chunkLength);
void constructImage();
void unfilterScanLine(byte *dest, const byte *scanLine, const byte *prevLine, uint16 byteWidth, byte filterType, uint16 length);
byte paethPredictor(int16 a, int16 b, int16 c);
// The original file stream
Common::SeekableReadStream *_stream;
// The unzipped image data stream
Common::SeekableReadStream *_imageData;
PNGHeader _header;
byte _palette[256 * 3]; // RGB
byte _paletteTransparency[256];
uint16 _paletteEntries;
uint16 _transparentColor[3];
bool _transparentColorSpecified;
byte *_compressedBuffer;
uint32 _compressedBufferSize;
Graphics::Surface *_outputSurface;
Graphics::PixelFormat findPixelFormat() const;
int getBytesPerPixel() const;
void constructOutput(const byte *surface);
};
} // End of namespace Graphics
#endif // GRAPHICS_PNG_H
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