/* 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