Mercurial > sdl-ios-xcode
annotate src/video/SDL_gamma.c @ 1495:1dd8bf30a109
Might have fixed 64-bit issues. :)
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sat, 11 Mar 2006 22:54:12 +0000 |
| parents | d910939febfa |
| children | 97d0966f4bf7 |
| 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 */ |
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22 #include "SDL_config.h" |
| 0 | 23 |
| 24 /* Gamma correction support */ | |
| 25 | |
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26 #ifdef HAVE_MATH_H |
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27 #include <math.h> /* Used for calculating gamma ramps */ |
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28 #else |
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29 /* Math routines from uClibc: http://www.uclibc.org */ |
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30 #include "math_private.h" |
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31 #include "e_sqrt.h" |
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32 #include "e_pow.h" |
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33 #include "e_log.h" |
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34 #define pow(x, y) __ieee754_pow(x, y) |
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35 #define log(x) __ieee754_log(x) |
| 0 | 36 #endif |
| 37 | |
| 38 #include "SDL_sysvideo.h" | |
| 39 | |
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40 |
| 0 | 41 static void CalculateGammaRamp(float gamma, Uint16 *ramp) |
| 42 { | |
| 43 int i; | |
| 44 | |
| 45 /* 0.0 gamma is all black */ | |
| 46 if ( gamma <= 0.0 ) { | |
| 47 for ( i=0; i<256; ++i ) { | |
| 48 ramp[i] = 0; | |
| 49 } | |
| 50 return; | |
| 51 } else | |
| 52 /* 1.0 gamma is identity */ | |
| 53 if ( gamma == 1.0 ) { | |
| 54 for ( i=0; i<256; ++i ) { | |
| 55 ramp[i] = (i << 8) | i; | |
| 56 } | |
| 57 return; | |
| 58 } else | |
| 59 /* Calculate a real gamma ramp */ | |
| 60 { int value; | |
| 61 gamma = 1.0f / gamma; | |
| 62 for ( i=0; i<256; ++i ) { | |
| 63 value = (int)(pow((double)i/256.0, gamma)*65535.0+0.5); | |
| 64 if ( value > 65535 ) { | |
| 65 value = 65535; | |
| 66 } | |
| 67 ramp[i] = (Uint16)value; | |
| 68 } | |
| 69 } | |
| 70 } | |
| 71 static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp) | |
| 72 { | |
| 73 /* The following is adapted from a post by Garrett Bass on OpenGL | |
| 74 Gamedev list, March 4, 2000. | |
| 75 */ | |
| 76 float sum = 0.0; | |
| 77 int i, count = 0; | |
| 78 | |
| 79 *gamma = 1.0; | |
| 80 for ( i = 1; i < 256; ++i ) { | |
| 81 if ( (ramp[i] != 0) && (ramp[i] != 65535) ) { | |
| 82 double B = (double)i / 256.0; | |
| 83 double A = ramp[i] / 65535.0; | |
| 84 sum += (float) ( log(A) / log(B) ); | |
| 85 count++; | |
| 86 } | |
| 87 } | |
| 88 if ( count && sum ) { | |
| 89 *gamma = 1.0f / (sum / count); | |
| 90 } | |
| 91 } | |
| 92 | |
| 93 int SDL_SetGamma(float red, float green, float blue) | |
| 94 { | |
| 95 int succeeded; | |
| 96 SDL_VideoDevice *video = current_video; | |
| 97 SDL_VideoDevice *this = current_video; | |
| 98 | |
| 99 succeeded = -1; | |
| 100 /* Prefer using SetGammaRamp(), as it's more flexible */ | |
| 101 { | |
| 102 Uint16 ramp[3][256]; | |
| 103 | |
| 104 CalculateGammaRamp(red, ramp[0]); | |
| 105 CalculateGammaRamp(green, ramp[1]); | |
| 106 CalculateGammaRamp(blue, ramp[2]); | |
| 107 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 108 } | |
| 109 if ( (succeeded < 0) && video->SetGamma ) { | |
| 110 SDL_ClearError(); | |
| 111 succeeded = video->SetGamma(this, red, green, blue); | |
| 112 } | |
| 113 return succeeded; | |
| 114 } | |
| 115 | |
| 116 /* Calculating the gamma by integrating the gamma ramps isn't exact, | |
| 117 so this function isn't officially supported. | |
| 118 */ | |
| 119 int SDL_GetGamma(float *red, float *green, float *blue) | |
| 120 { | |
| 121 int succeeded; | |
| 122 SDL_VideoDevice *video = current_video; | |
| 123 SDL_VideoDevice *this = current_video; | |
| 124 | |
| 125 succeeded = -1; | |
| 126 /* Prefer using GetGammaRamp(), as it's more flexible */ | |
| 127 { | |
| 128 Uint16 ramp[3][256]; | |
| 129 | |
| 130 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 131 if ( succeeded >= 0 ) { | |
| 132 CalculateGammaFromRamp(red, ramp[0]); | |
| 133 CalculateGammaFromRamp(green, ramp[1]); | |
| 134 CalculateGammaFromRamp(blue, ramp[2]); | |
| 135 } | |
| 136 } | |
| 137 if ( (succeeded < 0) && video->GetGamma ) { | |
| 138 SDL_ClearError(); | |
| 139 succeeded = video->GetGamma(this, red, green, blue); | |
| 140 } | |
| 141 return succeeded; | |
| 142 } | |
| 143 | |
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144 int SDL_SetGammaRamp(const Uint16 *red, const Uint16 *green, const Uint16 *blue) |
| 0 | 145 { |
| 146 int succeeded; | |
| 147 SDL_VideoDevice *video = current_video; | |
| 148 SDL_VideoDevice *this = current_video; | |
| 149 SDL_Surface *screen = SDL_PublicSurface; | |
| 150 | |
| 151 /* Verify the screen parameter */ | |
| 152 if ( !screen ) { | |
| 153 SDL_SetError("No video mode has been set"); | |
| 154 return -1; | |
| 155 } | |
| 156 | |
| 157 /* Lazily allocate the gamma tables */ | |
| 158 if ( ! video->gamma ) { | |
| 159 SDL_GetGammaRamp(0, 0, 0); | |
| 160 } | |
| 161 | |
| 162 /* Fill the gamma table with the new values */ | |
| 163 if ( red ) { | |
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164 SDL_memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); |
| 0 | 165 } |
| 166 if ( green ) { | |
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167 SDL_memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); |
| 0 | 168 } |
| 169 if ( blue ) { | |
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170 SDL_memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); |
| 0 | 171 } |
| 172 | |
| 173 /* Gamma correction always possible on split palettes */ | |
| 174 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { | |
| 175 SDL_Palette *pal = screen->format->palette; | |
| 176 | |
| 177 /* If physical palette has been set independently, use it */ | |
| 178 if(video->physpal) | |
| 179 pal = video->physpal; | |
| 180 | |
| 181 SDL_SetPalette(screen, SDL_PHYSPAL, | |
| 182 pal->colors, 0, pal->ncolors); | |
| 183 return 0; | |
| 184 } | |
| 185 | |
| 186 /* Try to set the gamma ramp in the driver */ | |
| 187 succeeded = -1; | |
| 188 if ( video->SetGammaRamp ) { | |
| 189 succeeded = video->SetGammaRamp(this, video->gamma); | |
| 190 } else { | |
| 191 SDL_SetError("Gamma ramp manipulation not supported"); | |
| 192 } | |
| 193 return succeeded; | |
| 194 } | |
| 195 | |
| 196 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
| 197 { | |
| 198 SDL_VideoDevice *video = current_video; | |
| 199 SDL_VideoDevice *this = current_video; | |
| 200 | |
| 201 /* Lazily allocate the gamma table */ | |
| 202 if ( ! video->gamma ) { | |
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203 video->gamma = SDL_malloc(3*256*sizeof(*video->gamma)); |
| 0 | 204 if ( ! video->gamma ) { |
| 205 SDL_OutOfMemory(); | |
| 206 return -1; | |
| 207 } | |
| 208 if ( video->GetGammaRamp ) { | |
| 209 /* Get the real hardware gamma */ | |
| 210 video->GetGammaRamp(this, video->gamma); | |
| 211 } else { | |
| 212 /* Assume an identity gamma */ | |
| 213 int i; | |
| 214 for ( i=0; i<256; ++i ) { | |
| 215 video->gamma[0*256+i] = (i << 8) | i; | |
| 216 video->gamma[1*256+i] = (i << 8) | i; | |
| 217 video->gamma[2*256+i] = (i << 8) | i; | |
| 218 } | |
| 219 } | |
| 220 } | |
| 221 | |
| 222 /* Just copy from our internal table */ | |
| 223 if ( red ) { | |
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224 SDL_memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); |
| 0 | 225 } |
| 226 if ( green ) { | |
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227 SDL_memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); |
| 0 | 228 } |
| 229 if ( blue ) { | |
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230 SDL_memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); |
| 0 | 231 } |
| 232 return 0; | |
| 233 } |