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https://github.com/w23/xash3d-fwgs
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88 lines
2.2 KiB
C
88 lines
2.2 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 texgammatable[256]; // palette is sent through this to convert to screen gamma
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static byte lightgammatable[256];
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static int lineargammatable[1024];
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static int screengammatable[1024];
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void BuildGammaTable( float lightgamma, float brightness )
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{
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int i, inf;
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float f, g, g1, g3;
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lightgamma = bound( 1.8f, lightgamma, 3.0f );
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brightness = bound( 0.0f, brightness, 10.0f );
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if( brightness <= 0.0f )
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g3 = 0.125f;
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else if( brightness > 1.0f )
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g3 = 0.05f;
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else g3 = 0.125f - (brightness * brightness) * 0.075f;
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g = 1.0f / lightgamma;
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g1 = GAMMA * g;
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for( i = 0; i < 256; i++ )
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{
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f = pow( i / 255.f, GAMMA );
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// scale up
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if( brightness > 1.0f )
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f = f * brightness;
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// shift up
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if( f <= g3 ) f = (f / g3) * 0.125f;
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else f = 0.125f + ((f - g3) / (1.0f - g3)) * 0.875f;
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// convert linear space to desired gamma space
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inf = (int)( 255.0 * pow( f, g ));
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lightgammatable[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, TEXGAMMA );
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inf = (int)(f + 0.5f);
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texgammatable[i] = bound( 0, inf, 255 );
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}
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for( i = 0; i < 1024; i++ )
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{
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// convert from screen gamma space to linear space
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lineargammatable[i] = 1023 * pow( i / 1023.0, g1 );
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// convert from linear gamma space to screen space
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screengammatable[i] = 1023 * pow( i / 1023.0, 1.0 / g1 );
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}
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}
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byte LightToTexGamma( byte b )
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{
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return lightgammatable[b];
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}
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byte TextureToGamma( byte b )
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{
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return texgammatable[b];
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} |