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90 lines
2.3 KiB
90 lines
2.3 KiB
/* |
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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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#ifdef HAVE_TGMATH_H |
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#include <tgmath.h> |
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#endif |
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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)( 255.0f * 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 = 255.0f * 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 / 1023.0f, g1 ); |
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// convert from linear gamma space to screen space |
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screengammatable[i] = 1023 * pow( i / 1023.0f, 1.0f / 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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}
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