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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.
*
* $URL$
* $Id$
*
*/
/*
* PNG decoder used in engines:
* - sword25
*/
#ifndef GRAPHICS_PNG_H
#define GRAPHICS_PNG_H
#include "graphics/surface.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.
namespace Common {
class SeekableReadStream;
}
namespace Graphics {
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;
};
struct PixelFormat;
class PNG {
public:
PNG();
~PNG();
/**
* Reads a PNG image from the specified stream
*/
bool read(Common::SeekableReadStream *str);
/**
* Returns the information obtained from the PNG header.
*/
PNGHeader getHeader() const { return _header; }
/**
* Returns the PNG image, formatted for the specified pixel format.
*/
Graphics::Surface *getSurface(const PixelFormat &format);
/**
* Returns the indexed PNG8 image. Used for PNGs with an indexed 256 color
* palette, when they're shown on an 8-bit color screen, as no translation
* is taking place.
*/
Graphics::Surface *getIndexedSurface() {
if (_header.colorType != kIndexed)
error("Indexed surface requested for a non-indexed PNG");
return _unfilteredSurface;
}
/**
* Returns the palette of the specified PNG8 image
*/
void getPalette(byte *palette, byte &entries) {
if (_header.colorType != kIndexed)
error("Palette requested for a non-indexed PNG");
palette = _palette;
entries = _paletteEntries;
}
private:
void readHeaderChunk();
byte getNumColorChannels();
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 * 4]; // RGBA
uint16 _paletteEntries;
uint16 _transparentColor[3];
bool _transparentColorSpecified;
byte *_compressedBuffer;
uint32 _compressedBufferSize;
Graphics::Surface *_unfilteredSurface;
};
} // End of Graphics namespace
#endif // GRAPHICS_PNG_H
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