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