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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 5131 | clevermous | 1 | /* |
| 2 | SDL - Simple DirectMedia Layer |
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| 3 | Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga |
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| 4 | |||
| 5 | This library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Library General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2 of the License, or (at your option) any later version. |
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| 9 | |||
| 10 | This library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Library General Public License for more details. |
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| 14 | |||
| 15 | You should have received a copy of the GNU Library General Public |
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| 16 | License along with this library; if not, write to the Free |
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| 17 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 18 | |||
| 19 | Sam Lantinga |
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| 20 | slouken@devolution.com |
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| 21 | */ |
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| 22 | |||
| 23 | |||
| 24 | /* Gamma correction support */ |
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| 25 | |||
| 26 | #define USE_MATH_H /* Used for calculating gamma ramps */ |
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| 27 | |||
| 28 | #ifdef USE_MATH_H |
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| 29 | #include |
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| 30 | #endif |
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| 31 | #include |
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| 32 | |||
| 33 | #include "SDL_error.h" |
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| 34 | #include "SDL_sysvideo.h" |
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| 35 | |||
| 36 | #ifdef USE_MATH_H |
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| 37 | static void CalculateGammaRamp(float gamma, Uint16 *ramp) |
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| 38 | { |
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| 39 | int i; |
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| 40 | |||
| 41 | /* 0.0 gamma is all black */ |
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| 42 | if ( gamma <= 0.0 ) { |
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| 43 | for ( i=0; i<256; ++i ) { |
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| 44 | ramp[i] = 0; |
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| 45 | } |
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| 46 | return; |
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| 47 | } else |
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| 48 | /* 1.0 gamma is identity */ |
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| 49 | if ( gamma == 1.0 ) { |
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| 50 | for ( i=0; i<256; ++i ) { |
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| 51 | ramp[i] = (i << 8) | i; |
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| 52 | } |
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| 53 | return; |
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| 54 | } else |
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| 55 | /* Calculate a real gamma ramp */ |
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| 56 | { int value; |
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| 57 | gamma = 1.0f / gamma; |
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| 58 | for ( i=0; i<256; ++i ) { |
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| 59 | value = (int)(pow((double)i/256.0, gamma)*65535.0+0.5); |
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| 60 | if ( value > 65535 ) { |
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| 61 | value = 65535; |
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| 62 | } |
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| 63 | ramp[i] = (Uint16)value; |
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| 64 | } |
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| 65 | } |
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| 66 | } |
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| 67 | static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp) |
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| 68 | { |
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| 69 | /* The following is adapted from a post by Garrett Bass on OpenGL |
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| 70 | Gamedev list, March 4, 2000. |
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| 71 | */ |
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| 72 | float sum = 0.0; |
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| 73 | int i, count = 0; |
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| 74 | |||
| 75 | *gamma = 1.0; |
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| 76 | for ( i = 1; i < 256; ++i ) { |
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| 77 | if ( (ramp[i] != 0) && (ramp[i] != 65535) ) { |
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| 78 | double B = (double)i / 256.0; |
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| 79 | double A = ramp[i] / 65535.0; |
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| 80 | sum += (float) ( log(A) / log(B) ); |
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| 81 | count++; |
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| 82 | } |
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| 83 | } |
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| 84 | if ( count && sum ) { |
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| 85 | *gamma = 1.0f / (sum / count); |
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| 86 | } |
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| 87 | } |
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| 88 | #endif /* USE_MATH_H */ |
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| 89 | |||
| 90 | int SDL_SetGamma(float red, float green, float blue) |
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| 91 | { |
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| 92 | int succeeded; |
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| 93 | SDL_VideoDevice *video = current_video; |
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| 94 | SDL_VideoDevice *this = current_video; |
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| 95 | |||
| 96 | succeeded = -1; |
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| 97 | #ifdef USE_MATH_H |
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| 98 | /* Prefer using SetGammaRamp(), as it's more flexible */ |
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| 99 | { |
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| 100 | Uint16 ramp[3][256]; |
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| 101 | |||
| 102 | CalculateGammaRamp(red, ramp[0]); |
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| 103 | CalculateGammaRamp(green, ramp[1]); |
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| 104 | CalculateGammaRamp(blue, ramp[2]); |
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| 105 | succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); |
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| 106 | } |
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| 107 | #else |
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| 108 | SDL_SetError("Gamma correction not supported"); |
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| 109 | #endif |
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| 110 | if ( (succeeded < 0) && video->SetGamma ) { |
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| 111 | SDL_ClearError(); |
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| 112 | succeeded = video->SetGamma(this, red, green, blue); |
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| 113 | } |
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| 114 | return succeeded; |
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| 115 | } |
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| 116 | |||
| 117 | /* Calculating the gamma by integrating the gamma ramps isn't exact, |
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| 118 | so this function isn't officially supported. |
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| 119 | */ |
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| 120 | int SDL_GetGamma(float *red, float *green, float *blue) |
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| 121 | { |
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| 122 | int succeeded; |
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| 123 | SDL_VideoDevice *video = current_video; |
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| 124 | SDL_VideoDevice *this = current_video; |
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| 125 | |||
| 126 | succeeded = -1; |
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| 127 | #ifdef USE_MATH_H |
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| 128 | /* Prefer using GetGammaRamp(), as it's more flexible */ |
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| 129 | { |
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| 130 | Uint16 ramp[3][256]; |
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| 131 | |||
| 132 | succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); |
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| 133 | if ( succeeded >= 0 ) { |
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| 134 | CalculateGammaFromRamp(red, ramp[0]); |
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| 135 | CalculateGammaFromRamp(green, ramp[1]); |
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| 136 | CalculateGammaFromRamp(blue, ramp[2]); |
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| 137 | } |
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| 138 | } |
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| 139 | #else |
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| 140 | SDL_SetError("Gamma correction not supported"); |
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| 141 | #endif |
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| 142 | if ( (succeeded < 0) && video->GetGamma ) { |
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| 143 | SDL_ClearError(); |
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| 144 | succeeded = video->GetGamma(this, red, green, blue); |
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| 145 | } |
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| 146 | return succeeded; |
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| 147 | } |
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| 148 | |||
| 149 | int SDL_SetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) |
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| 150 | { |
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| 151 | int succeeded; |
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| 152 | SDL_VideoDevice *video = current_video; |
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| 153 | SDL_VideoDevice *this = current_video; |
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| 154 | SDL_Surface *screen = SDL_PublicSurface; |
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| 155 | |||
| 156 | /* Verify the screen parameter */ |
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| 157 | if ( !screen ) { |
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| 158 | SDL_SetError("No video mode has been set"); |
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| 159 | return -1; |
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| 160 | } |
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| 161 | |||
| 162 | /* Lazily allocate the gamma tables */ |
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| 163 | if ( ! video->gamma ) { |
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| 164 | SDL_GetGammaRamp(0, 0, 0); |
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| 165 | } |
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| 166 | |||
| 167 | /* Fill the gamma table with the new values */ |
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| 168 | if ( red ) { |
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| 169 | memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); |
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| 170 | } |
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| 171 | if ( green ) { |
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| 172 | memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); |
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| 173 | } |
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| 174 | if ( blue ) { |
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| 175 | memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); |
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| 176 | } |
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| 177 | |||
| 178 | /* Gamma correction always possible on split palettes */ |
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| 179 | if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { |
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| 180 | SDL_Palette *pal = screen->format->palette; |
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| 181 | |||
| 182 | /* If physical palette has been set independently, use it */ |
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| 183 | if(video->physpal) |
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| 184 | pal = video->physpal; |
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| 185 | |||
| 186 | SDL_SetPalette(screen, SDL_PHYSPAL, |
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| 187 | pal->colors, 0, pal->ncolors); |
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| 188 | return 0; |
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| 189 | } |
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| 190 | |||
| 191 | /* Try to set the gamma ramp in the driver */ |
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| 192 | succeeded = -1; |
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| 193 | if ( video->SetGammaRamp ) { |
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| 194 | succeeded = video->SetGammaRamp(this, video->gamma); |
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| 195 | } else { |
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| 196 | SDL_SetError("Gamma ramp manipulation not supported"); |
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| 197 | } |
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| 198 | return succeeded; |
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| 199 | } |
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| 200 | |||
| 201 | int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) |
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| 202 | { |
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| 203 | SDL_VideoDevice *video = current_video; |
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| 204 | SDL_VideoDevice *this = current_video; |
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| 205 | |||
| 206 | /* Lazily allocate the gamma table */ |
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| 207 | if ( ! video->gamma ) { |
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| 208 | video->gamma = malloc(3*256*sizeof(*video->gamma)); |
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| 209 | if ( ! video->gamma ) { |
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| 210 | SDL_OutOfMemory(); |
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| 211 | return -1; |
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| 212 | } |
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| 213 | if ( video->GetGammaRamp ) { |
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| 214 | /* Get the real hardware gamma */ |
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| 215 | video->GetGammaRamp(this, video->gamma); |
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| 216 | } else { |
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| 217 | /* Assume an identity gamma */ |
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| 218 | int i; |
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| 219 | for ( i=0; i<256; ++i ) { |
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| 220 | video->gamma[0*256+i] = (i << 8) | i; |
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| 221 | video->gamma[1*256+i] = (i << 8) | i; |
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| 222 | video->gamma[2*256+i] = (i << 8) | i; |
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| 223 | } |
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| 224 | } |
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| 225 | } |
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| 226 | |||
| 227 | /* Just copy from our internal table */ |
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| 228 | if ( red ) { |
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| 229 | memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); |
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| 230 | } |
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| 231 | if ( green ) { |
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| 232 | memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); |
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| 233 | } |
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| 234 | if ( blue ) { |
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| 235 | memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); |
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| 236 | } |
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| 237 | return 0; |
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| 238 | } |