Mercurial > sdl-ios-xcode
annotate src/video/SDL_gamma.c @ 1378:dc0e13e7e1ae
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| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 19 Feb 2006 23:38:57 +0000 |
| parents | c71e05b4dc2e |
| children | d910939febfa |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 SDL - Simple DirectMedia Layer | |
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3 Copyright (C) 1997-2006 Sam Lantinga |
| 0 | 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 Lesser General Public |
| 0 | 7 License as published by the Free Software Foundation; either |
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8 version 2.1 of the License, or (at your option) any later version. |
| 0 | 9 |
| 10 This library is distributed in the hope that it will be useful, | |
| 11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
|
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13 Lesser General Public License for more details. |
| 0 | 14 |
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15 You should have received a copy of the GNU Lesser General Public |
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16 License along with this library; if not, write to the Free Software |
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 0 | 18 |
| 19 Sam Lantinga | |
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20 slouken@libsdl.org |
| 0 | 21 */ |
| 22 | |
| 23 /* Gamma correction support */ | |
| 24 | |
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25 #include "SDL_config.h" |
| 0 | 26 |
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27 #ifdef HAVE_MATH_H |
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28 #include <math.h> /* Used for calculating gamma ramps */ |
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29 #else |
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30 /* Math routines from uClibc: http://www.uclibc.org */ |
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31 #include "math_private.h" |
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32 #include "e_sqrt.h" |
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33 #include "e_pow.h" |
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34 #include "e_log.h" |
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35 #define pow(x, y) __ieee754_pow(x, y) |
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36 #define log(x) __ieee754_log(x) |
| 0 | 37 #endif |
| 38 | |
| 39 #include "SDL_sysvideo.h" | |
| 40 | |
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41 |
| 0 | 42 static void CalculateGammaRamp(float gamma, Uint16 *ramp) |
| 43 { | |
| 44 int i; | |
| 45 | |
| 46 /* 0.0 gamma is all black */ | |
| 47 if ( gamma <= 0.0 ) { | |
| 48 for ( i=0; i<256; ++i ) { | |
| 49 ramp[i] = 0; | |
| 50 } | |
| 51 return; | |
| 52 } else | |
| 53 /* 1.0 gamma is identity */ | |
| 54 if ( gamma == 1.0 ) { | |
| 55 for ( i=0; i<256; ++i ) { | |
| 56 ramp[i] = (i << 8) | i; | |
| 57 } | |
| 58 return; | |
| 59 } else | |
| 60 /* Calculate a real gamma ramp */ | |
| 61 { int value; | |
| 62 gamma = 1.0f / gamma; | |
| 63 for ( i=0; i<256; ++i ) { | |
| 64 value = (int)(pow((double)i/256.0, gamma)*65535.0+0.5); | |
| 65 if ( value > 65535 ) { | |
| 66 value = 65535; | |
| 67 } | |
| 68 ramp[i] = (Uint16)value; | |
| 69 } | |
| 70 } | |
| 71 } | |
| 72 static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp) | |
| 73 { | |
| 74 /* The following is adapted from a post by Garrett Bass on OpenGL | |
| 75 Gamedev list, March 4, 2000. | |
| 76 */ | |
| 77 float sum = 0.0; | |
| 78 int i, count = 0; | |
| 79 | |
| 80 *gamma = 1.0; | |
| 81 for ( i = 1; i < 256; ++i ) { | |
| 82 if ( (ramp[i] != 0) && (ramp[i] != 65535) ) { | |
| 83 double B = (double)i / 256.0; | |
| 84 double A = ramp[i] / 65535.0; | |
| 85 sum += (float) ( log(A) / log(B) ); | |
| 86 count++; | |
| 87 } | |
| 88 } | |
| 89 if ( count && sum ) { | |
| 90 *gamma = 1.0f / (sum / count); | |
| 91 } | |
| 92 } | |
| 93 | |
| 94 int SDL_SetGamma(float red, float green, float blue) | |
| 95 { | |
| 96 int succeeded; | |
| 97 SDL_VideoDevice *video = current_video; | |
| 98 SDL_VideoDevice *this = current_video; | |
| 99 | |
| 100 succeeded = -1; | |
| 101 /* Prefer using SetGammaRamp(), as it's more flexible */ | |
| 102 { | |
| 103 Uint16 ramp[3][256]; | |
| 104 | |
| 105 CalculateGammaRamp(red, ramp[0]); | |
| 106 CalculateGammaRamp(green, ramp[1]); | |
| 107 CalculateGammaRamp(blue, ramp[2]); | |
| 108 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 109 } | |
| 110 if ( (succeeded < 0) && video->SetGamma ) { | |
| 111 SDL_ClearError(); | |
| 112 succeeded = video->SetGamma(this, red, green, blue); | |
| 113 } | |
| 114 return succeeded; | |
| 115 } | |
| 116 | |
| 117 /* Calculating the gamma by integrating the gamma ramps isn't exact, | |
| 118 so this function isn't officially supported. | |
| 119 */ | |
| 120 int SDL_GetGamma(float *red, float *green, float *blue) | |
| 121 { | |
| 122 int succeeded; | |
| 123 SDL_VideoDevice *video = current_video; | |
| 124 SDL_VideoDevice *this = current_video; | |
| 125 | |
| 126 succeeded = -1; | |
| 127 /* Prefer using GetGammaRamp(), as it's more flexible */ | |
| 128 { | |
| 129 Uint16 ramp[3][256]; | |
| 130 | |
| 131 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 132 if ( succeeded >= 0 ) { | |
| 133 CalculateGammaFromRamp(red, ramp[0]); | |
| 134 CalculateGammaFromRamp(green, ramp[1]); | |
| 135 CalculateGammaFromRamp(blue, ramp[2]); | |
| 136 } | |
| 137 } | |
| 138 if ( (succeeded < 0) && video->GetGamma ) { | |
| 139 SDL_ClearError(); | |
| 140 succeeded = video->GetGamma(this, red, green, blue); | |
| 141 } | |
| 142 return succeeded; | |
| 143 } | |
| 144 | |
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145 int SDL_SetGammaRamp(const Uint16 *red, const Uint16 *green, const Uint16 *blue) |
| 0 | 146 { |
| 147 int succeeded; | |
| 148 SDL_VideoDevice *video = current_video; | |
| 149 SDL_VideoDevice *this = current_video; | |
| 150 SDL_Surface *screen = SDL_PublicSurface; | |
| 151 | |
| 152 /* Verify the screen parameter */ | |
| 153 if ( !screen ) { | |
| 154 SDL_SetError("No video mode has been set"); | |
| 155 return -1; | |
| 156 } | |
| 157 | |
| 158 /* Lazily allocate the gamma tables */ | |
| 159 if ( ! video->gamma ) { | |
| 160 SDL_GetGammaRamp(0, 0, 0); | |
| 161 } | |
| 162 | |
| 163 /* Fill the gamma table with the new values */ | |
| 164 if ( red ) { | |
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165 SDL_memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); |
| 0 | 166 } |
| 167 if ( green ) { | |
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168 SDL_memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); |
| 0 | 169 } |
| 170 if ( blue ) { | |
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171 SDL_memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); |
| 0 | 172 } |
| 173 | |
| 174 /* Gamma correction always possible on split palettes */ | |
| 175 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { | |
| 176 SDL_Palette *pal = screen->format->palette; | |
| 177 | |
| 178 /* If physical palette has been set independently, use it */ | |
| 179 if(video->physpal) | |
| 180 pal = video->physpal; | |
| 181 | |
| 182 SDL_SetPalette(screen, SDL_PHYSPAL, | |
| 183 pal->colors, 0, pal->ncolors); | |
| 184 return 0; | |
| 185 } | |
| 186 | |
| 187 /* Try to set the gamma ramp in the driver */ | |
| 188 succeeded = -1; | |
| 189 if ( video->SetGammaRamp ) { | |
| 190 succeeded = video->SetGammaRamp(this, video->gamma); | |
| 191 } else { | |
| 192 SDL_SetError("Gamma ramp manipulation not supported"); | |
| 193 } | |
| 194 return succeeded; | |
| 195 } | |
| 196 | |
| 197 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
| 198 { | |
| 199 SDL_VideoDevice *video = current_video; | |
| 200 SDL_VideoDevice *this = current_video; | |
| 201 | |
| 202 /* Lazily allocate the gamma table */ | |
| 203 if ( ! video->gamma ) { | |
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204 video->gamma = SDL_malloc(3*256*sizeof(*video->gamma)); |
| 0 | 205 if ( ! video->gamma ) { |
| 206 SDL_OutOfMemory(); | |
| 207 return -1; | |
| 208 } | |
| 209 if ( video->GetGammaRamp ) { | |
| 210 /* Get the real hardware gamma */ | |
| 211 video->GetGammaRamp(this, video->gamma); | |
| 212 } else { | |
| 213 /* Assume an identity gamma */ | |
| 214 int i; | |
| 215 for ( i=0; i<256; ++i ) { | |
| 216 video->gamma[0*256+i] = (i << 8) | i; | |
| 217 video->gamma[1*256+i] = (i << 8) | i; | |
| 218 video->gamma[2*256+i] = (i << 8) | i; | |
| 219 } | |
| 220 } | |
| 221 } | |
| 222 | |
| 223 /* Just copy from our internal table */ | |
| 224 if ( red ) { | |
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225 SDL_memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); |
| 0 | 226 } |
| 227 if ( green ) { | |
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228 SDL_memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); |
| 0 | 229 } |
| 230 if ( blue ) { | |
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231 SDL_memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); |
| 0 | 232 } |
| 233 return 0; | |
| 234 } |