68 lines
1.7 KiB
C
68 lines
1.7 KiB
C
/*
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gamma.c - gamma routines
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Copyright (C) 2011 Uncle Mike
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(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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*/
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#include "common.h"
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#include <mathlib.h>
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#include "gl_local.h"
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//-----------------------------------------------------------------------------
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// Gamma conversion support
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//-----------------------------------------------------------------------------
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static byte gammatable[256];
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static byte texgammatable[256]; // palette is sent through this to convert to screen gamma
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void BuildGammaTable( float gamma, float texGamma )
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{
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int i, inf;
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float g1, g = gamma;
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double f;
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g = bound( 1.8f, g, 3.0f );
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texGamma = bound( 1.8f, texGamma, 3.0f );
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g = 1.0f / g;
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g1 = texGamma * g;
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for( i = 0; i < 256; i++ )
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{
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inf = 255 * pow( i / 255.f, g1 );
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texgammatable[i] = bound( 0, inf, 255 );
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}
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for( i = 0; i < 256; i++ )
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{
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f = 255.0 * pow(( float )i / 255.0f, 2.2f / texGamma );
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inf = (int)(f + 0.5f);
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gammatable[i] = bound( 0, inf, 255 );
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}
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}
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byte TextureToTexGamma( byte b )
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{
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if( glConfig.deviceSupportsGamma )
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return b; // passthrough
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b = bound( 0, b, 255 );
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return texgammatable[b];
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}
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byte TextureToGamma( byte b )
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{
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if( glConfig.deviceSupportsGamma )
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return b; // passthrough
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b = bound( 0, b, 255 );
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return gammatable[b];
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} |