/* 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.
 *
 * $URL$
 * $Id$
 *
 */

#ifndef GRAPHICS_COLORMASKS_H
#define GRAPHICS_COLORMASKS_H

namespace Graphics {

template<int bitFormat>
struct ColorMasks {
};

/*
The ColorMasks template can be used to map bit format values
(like 555, 565, 1555, 4444) to corresponding bit masks and shift values.
Currently this is only meant for

The meaning of these is masks is the following:
 kBytesPerPixel
    -> how many bytes per pixel for that format

 kRedMask, kGreenMask, kBlueMask
    -> bitmask, and this with the color to select only the bits of the corresponding color

 The k*Bits and k*Shift values can be used to extract R,G,B. I.e. to get
 the red color component of a pixel, as a 8-bit value, you would write

 R = ((color & kRedMask) >> kRedShift) << (8-kRedBits)

 Actually, instead of the simple left shift, one might want to use somewhat
 more sophisticated code (which fills up the least significant bits with
 appropriate data).


 The highBits / lowBits / qhighBits / qlowBits are special values that are
 used in the super-optimized interpolation functions in scaler/intern.h
 and scaler/aspect.cpp. Currently they are only available in 555 and 565 mode.
 To be specific: They pack the masks for two 16 bit pixels at once. The pixels
 are split into "high" and "low" bits, which are then separately interpolated
 and finally re-composed. That way, 2x2 pixels or even 4x2 pixels can
 be interpolated in one go.

*/


template<>
struct ColorMasks<565> {
	enum {
		highBits    = 0xF7DEF7DE,
		lowBits     = 0x08210821,
		qhighBits   = 0xE79CE79C,
		qlowBits    = 0x18631863,


		kBytesPerPixel = 2,

		kAlphaBits  = 0,
		kRedBits    = 5,
		kGreenBits  = 6,
		kBlueBits   = 5,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask

	};
};

template<>
struct ColorMasks<555> {
	enum {
		highBits    = 0x7BDE7BDE,
		lowBits     = 0x04210421,
		qhighBits   = 0x739C739C,
		qlowBits    = 0x0C630C63,


		kBytesPerPixel = 2,

		kAlphaBits  = 0,
		kRedBits    = 5,
		kGreenBits  = 5,
		kBlueBits   = 5,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask
	};
};

template<>
struct ColorMasks<1555> {
	enum {
		kBytesPerPixel = 2,

		kAlphaBits  = 1,
		kRedBits    = 5,
		kGreenBits  = 5,
		kBlueBits   = 5,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask
	};
};

template<>
struct ColorMasks<4444> {
	enum {
		kBytesPerPixel = 2,

		kAlphaBits  = 4,
		kRedBits    = 4,
		kGreenBits  = 4,
		kBlueBits   = 4,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask
	};
};

template<>
struct ColorMasks<888> {
	enum {
		kBytesPerPixel = 4,

		kAlphaBits  = 0,
		kRedBits    = 8,
		kGreenBits  = 8,
		kBlueBits   = 8,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask
	};
};

template<>
struct ColorMasks<8888> {
	enum {
		kBytesPerPixel = 4,

		kAlphaBits  = 8,
		kRedBits    = 8,
		kGreenBits  = 8,
		kBlueBits   = 8,

		kAlphaShift = kRedBits+kGreenBits+kBlueBits,
		kRedShift   = kGreenBits+kBlueBits,
		kGreenShift = kBlueBits,
		kBlueShift  = 0,

		kAlphaMask = ((1 << kAlphaBits) - 1) << kAlphaShift,
		kRedMask   = ((1 << kRedBits) - 1) << kRedShift,
		kGreenMask = ((1 << kGreenBits) - 1) << kGreenShift,
		kBlueMask  = ((1 << kBlueBits) - 1) << kBlueShift,

		kRedBlueMask = kRedMask | kBlueMask
	};
};

template<class T>
uint32 RGBToColor(uint8 r, uint8 g, uint8 b) {
	return T::kAlphaMask |
	       (((r << T::kRedShift) >> (8 - T::kRedBits)) & T::kRedMask) |
	       (((g << T::kGreenShift) >> (8 - T::kGreenBits)) & T::kGreenMask) |
	       (((b << T::kBlueShift) >> (8 - T::kBlueBits)) & T::kBlueMask);
}

template<class T>
uint32 ARGBToColor(uint8 a, uint8 r, uint8 g, uint8 b) {
	return (((a << T::kAlphaShift) >> (8 - T::kAlphaBits)) & T::kAlphaMask) |
	       (((r << T::kRedShift) >> (8 - T::kRedBits)) & T::kRedMask) |
	       (((g << T::kGreenShift) >> (8 - T::kGreenBits)) & T::kGreenMask) |
	       (((b << T::kBlueShift) >> (8 - T::kBlueBits)) & T::kBlueMask);
}

template<class T>
void colorToRGB(uint32 color, uint8 &r, uint8 &g, uint8 &b) {
	r = ((color & T::kRedMask) >> T::kRedShift) << (8 - T::kRedBits);
	g = ((color & T::kGreenMask) >> T::kGreenShift) << (8 - T::kGreenBits);
	b = ((color & T::kBlueMask) >> T::kBlueShift) << (8 - T::kBlueBits);
}

template<class T>
void colorToARGB(uint32 color, uint8 &a, uint8 &r, uint8 &g, uint8 &b) {
	a = ((color & T::kAlphaMask) >> T::kAlphaShift) << (8 - T::kAlphaBits);
	r = ((color & T::kRedMask) >> T::kRedShift) << (8 - T::kRedBits);
	g = ((color & T::kGreenMask) >> T::kGreenShift) << (8 - T::kGreenBits);
	b = ((color & T::kBlueMask) >> T::kBlueShift) << (8 - T::kBlueBits);
}

/**
 * A pixel format description.
 *
 * Like ColorMasks it includes the given values to create colors from RGB
 * values and to retrieve RGB values from colors.
 *
 * Unlike ColorMasks it is not dependend on knowing the exact pixel format
 * on compile time.
 *
 * A minor difference between ColorMasks and PixelFormat is that ColorMasks
 * stores the bit count per channel in 'kFooBits', while PixelFormat stores
 * the loss compared to 8 bits per channel in '#Loss'.
 */
struct PixelFormat {
	byte bytesPerPixel; /**< Number of bytes used in the pixel format. */

	byte rLoss, gLoss, bLoss, aLoss; /**< Precision loss of each color component. */
	byte rShift, gShift, bShift, aShift; /**< Binary left shift of each color component in the pixel value. */

	uint32 rMask, gMask, bMask, aMask; /**< Binary mask used to retrieve individual color values. */
};

template<class Mask>
PixelFormat createPixelFormatFromMask() {
	PixelFormat format;

	format.bytesPerPixel = Mask::kBytesPerPixel;

	format.rLoss = 8 - Mask::kRedBits;
	format.gLoss = 8 - Mask::kGreenBits;
	format.bLoss = 8 - Mask::kBlueBits;
	format.aLoss = 8 - Mask::kAlphaBits;

	format.rShift = Mask::kRedShift;
	format.gShift = Mask::kGreenShift;
	format.bShift = Mask::kBlueShift;
	format.aShift = Mask::kAlphaShift;

	return format;
}

inline uint32 RGBToColor(uint8 r, uint8 g, uint8 b, const PixelFormat &fmt) {
	return
		((0xFF >> fmt.aLoss) << fmt.aShift) |
		((   r >> fmt.rLoss) << fmt.rShift) |
		((   g >> fmt.gLoss) << fmt.gShift) |
		((   b >> fmt.bLoss) << fmt.bShift);
}

inline uint32 ARGBToColor(uint8 a, uint8 r, uint8 g, uint8 b, const PixelFormat &fmt) {
	return
		((a >> fmt.aLoss) << fmt.aShift) |
		((r >> fmt.rLoss) << fmt.rShift) |
		((g >> fmt.gLoss) << fmt.gShift) |
		((b >> fmt.bLoss) << fmt.bShift);
}

inline void colorToRGB(uint32 color, uint8 &r, uint8 &g, uint8 &b, const PixelFormat &fmt) {
	r = ((color >> fmt.rShift) << fmt.rLoss) & 0xFF;
	g = ((color >> fmt.gShift) << fmt.gLoss) & 0xFF;
	b = ((color >> fmt.bShift) << fmt.bLoss) & 0xFF;
}

inline void colorToARGB(uint32 color, uint8 &a, uint8 &r, uint8 &g, uint8 &b, const PixelFormat &fmt) {
	a = ((color >> fmt.aShift) << fmt.aLoss) & 0xFF;
	r = ((color >> fmt.rShift) << fmt.rLoss) & 0xFF;
	g = ((color >> fmt.gShift) << fmt.gLoss) & 0xFF;
	b = ((color >> fmt.bShift) << fmt.bLoss) & 0xFF;
}

} // end of namespace Graphics

#endif