raze-gles/source/common/textures/imagehelpers.cpp

/*
 ** imagehelpers.cpp
 ** Utilities for image conversion - mostly 8 bit paletted baggage
 **
 **---------------------------------------------------------------------------
 ** Copyright 2004-2007 Randy Heit
 ** Copyright 2006-2018 Christoph Oelckers
 ** All rights reserved.
 **
 ** Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions
 ** are met:
 **
 ** 1. Redistributions of source code must retain the above copyright
 **    notice, this list of conditions and the following disclaimer.
 ** 2. Redistributions in binary form must reproduce the above copyright
 **    notice, this list of conditions and the following disclaimer in the
 **    documentation and/or other materials provided with the distribution.
 ** 3. The name of the author may not be used to endorse or promote products
 **    derived from this software without specific prior written permission.
 **
 ** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 ** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 ** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 ** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 ** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 ** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 **---------------------------------------------------------------------------
 **
 **
 */
 
 #include "imagehelpers.h"

namespace ImageHelpers
{
	uint8_t GrayMap[256];
	PalEntry BaseColors[256];
	PalEntry BasePalette[256];	// same as above, but with a being a proper alpha channel.
	int WhiteIndex, BlackIndex;
	int alphaThreshold;
	ColorTable256k RGB256k;

	int BestColor(int r, int g, int b, int first, int num)
	{
		const PalEntry* pal = BaseColors;
		int bestcolor = first;
		int bestdist = 257 * 257 + 257 * 257 + 257 * 257;

		for (int color = first; color < num; color++)
		{
			if (pal[color].a > 0) continue;	// marks a fullbright color which we should not pick here
			int x = r - pal[color].r;
			int y = g - pal[color].g;
			int z = b - pal[color].b;
			int dist = x * x + y * y + z * z;
			if (dist < bestdist)
			{
				if (dist == 0)
					return color;

				bestdist = dist;
				bestcolor = color;
			}
		}
		return bestcolor;
	}

	
	void SetPalette(const PalEntry* colors)
	{
		for (int i = 0; i < 255; i++)
		{
			BasePalette[i] = BaseColors[i] = colors[i];
			BasePalette[i].a = 255;
		}
		BasePalette[255] = BaseColors[255] = 0;	// 255 is always translucent black - whatever color the original data has here

		// Find white and black from the original palette so that they can be
		// used to make an educated guess of the translucency % for a
		// translucency map.
		WhiteIndex = BestColor(255, 255, 255);
		BlackIndex = BestColor(0, 0, 0);

		// create the RGB666 lookup table
		for (int r = 0; r < 64; r++)
			for (int g = 0; g < 64; g++)
				for (int b = 0; b < 64; b++)
					RGB256k.RGB[r][g][b] = BestColor((r<<2)|(r>>4), (g<<2)|(g>>4), (b<<2)|(b>>4));
	}
	
	
}