Mercurial > sdl-ios-xcode
annotate src/video/SDL_gamma.c @ 513:8feff52d7f5f
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| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 06 Oct 2002 18:47:20 +0000 |
| parents | f6ffac90895c |
| children | 37bb90b3d976 |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 SDL - Simple DirectMedia Layer | |
|
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f6ffac90895c
Updated copyright information for 2002
Sam Lantinga <slouken@libsdl.org>
parents:
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3 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002 Sam Lantinga |
| 0 | 4 |
| 5 This library is free software; you can redistribute it and/or | |
| 6 modify it under the terms of the GNU Library General Public | |
| 7 License as published by the Free Software Foundation; either | |
| 8 version 2 of the License, or (at your option) any later version. | |
| 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 | |
| 13 Library General Public License for more details. | |
| 14 | |
| 15 You should have received a copy of the GNU Library General Public | |
| 16 License along with this library; if not, write to the Free | |
| 17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 18 | |
| 19 Sam Lantinga | |
|
252
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Updated the source with the correct e-mail address
Sam Lantinga <slouken@libsdl.org>
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changeset
|
20 slouken@libsdl.org |
| 0 | 21 */ |
| 22 | |
| 23 #ifdef SAVE_RCSID | |
| 24 static char rcsid = | |
| 25 "@(#) $Id$"; | |
| 26 #endif | |
| 27 | |
| 28 /* Gamma correction support */ | |
| 29 | |
| 30 #define USE_MATH_H /* Used for calculating gamma ramps */ | |
| 31 | |
| 32 #ifdef USE_MATH_H | |
| 33 #include <math.h> | |
| 34 #endif | |
| 35 #include <stdlib.h> | |
| 152 | 36 #include <string.h> |
| 0 | 37 |
| 38 #include "SDL_error.h" | |
| 39 #include "SDL_sysvideo.h" | |
| 40 | |
| 41 #ifdef USE_MATH_H | |
| 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 #endif /* USE_MATH_H */ | |
| 94 | |
| 95 int SDL_SetGamma(float red, float green, float blue) | |
| 96 { | |
| 97 int succeeded; | |
| 98 SDL_VideoDevice *video = current_video; | |
| 99 SDL_VideoDevice *this = current_video; | |
| 100 | |
| 101 succeeded = -1; | |
| 102 #ifdef USE_MATH_H | |
| 103 /* Prefer using SetGammaRamp(), as it's more flexible */ | |
| 104 { | |
| 105 Uint16 ramp[3][256]; | |
| 106 | |
| 107 CalculateGammaRamp(red, ramp[0]); | |
| 108 CalculateGammaRamp(green, ramp[1]); | |
| 109 CalculateGammaRamp(blue, ramp[2]); | |
| 110 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 111 } | |
| 112 #else | |
| 113 SDL_SetError("Gamma correction not supported"); | |
| 114 #endif | |
| 115 if ( (succeeded < 0) && video->SetGamma ) { | |
| 116 SDL_ClearError(); | |
| 117 succeeded = video->SetGamma(this, red, green, blue); | |
| 118 } | |
| 119 return succeeded; | |
| 120 } | |
| 121 | |
| 122 /* Calculating the gamma by integrating the gamma ramps isn't exact, | |
| 123 so this function isn't officially supported. | |
| 124 */ | |
| 125 int SDL_GetGamma(float *red, float *green, float *blue) | |
| 126 { | |
| 127 int succeeded; | |
| 128 SDL_VideoDevice *video = current_video; | |
| 129 SDL_VideoDevice *this = current_video; | |
| 130 | |
| 131 succeeded = -1; | |
| 132 #ifdef USE_MATH_H | |
| 133 /* Prefer using GetGammaRamp(), as it's more flexible */ | |
| 134 { | |
| 135 Uint16 ramp[3][256]; | |
| 136 | |
| 137 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
| 138 if ( succeeded >= 0 ) { | |
| 139 CalculateGammaFromRamp(red, ramp[0]); | |
| 140 CalculateGammaFromRamp(green, ramp[1]); | |
| 141 CalculateGammaFromRamp(blue, ramp[2]); | |
| 142 } | |
| 143 } | |
| 144 #else | |
| 145 SDL_SetError("Gamma correction not supported"); | |
| 146 #endif | |
| 147 if ( (succeeded < 0) && video->GetGamma ) { | |
| 148 SDL_ClearError(); | |
| 149 succeeded = video->GetGamma(this, red, green, blue); | |
| 150 } | |
| 151 return succeeded; | |
| 152 } | |
| 153 | |
| 154 int SDL_SetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
| 155 { | |
| 156 int succeeded; | |
| 157 SDL_VideoDevice *video = current_video; | |
| 158 SDL_VideoDevice *this = current_video; | |
| 159 SDL_Surface *screen = SDL_PublicSurface; | |
| 160 | |
| 161 /* Verify the screen parameter */ | |
| 162 if ( !screen ) { | |
| 163 SDL_SetError("No video mode has been set"); | |
| 164 return -1; | |
| 165 } | |
| 166 | |
| 167 /* Lazily allocate the gamma tables */ | |
| 168 if ( ! video->gamma ) { | |
| 169 SDL_GetGammaRamp(0, 0, 0); | |
| 170 } | |
| 171 | |
| 172 /* Fill the gamma table with the new values */ | |
| 173 if ( red ) { | |
| 174 memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); | |
| 175 } | |
| 176 if ( green ) { | |
| 177 memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); | |
| 178 } | |
| 179 if ( blue ) { | |
| 180 memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); | |
| 181 } | |
| 182 | |
| 183 /* Gamma correction always possible on split palettes */ | |
| 184 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { | |
| 185 SDL_Palette *pal = screen->format->palette; | |
| 186 | |
| 187 /* If physical palette has been set independently, use it */ | |
| 188 if(video->physpal) | |
| 189 pal = video->physpal; | |
| 190 | |
| 191 SDL_SetPalette(screen, SDL_PHYSPAL, | |
| 192 pal->colors, 0, pal->ncolors); | |
| 193 return 0; | |
| 194 } | |
| 195 | |
| 196 /* Try to set the gamma ramp in the driver */ | |
| 197 succeeded = -1; | |
| 198 if ( video->SetGammaRamp ) { | |
| 199 succeeded = video->SetGammaRamp(this, video->gamma); | |
| 200 } else { | |
| 201 SDL_SetError("Gamma ramp manipulation not supported"); | |
| 202 } | |
| 203 return succeeded; | |
| 204 } | |
| 205 | |
| 206 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
| 207 { | |
| 208 SDL_VideoDevice *video = current_video; | |
| 209 SDL_VideoDevice *this = current_video; | |
| 210 | |
| 211 /* Lazily allocate the gamma table */ | |
| 212 if ( ! video->gamma ) { | |
| 213 video->gamma = malloc(3*256*sizeof(*video->gamma)); | |
| 214 if ( ! video->gamma ) { | |
| 215 SDL_OutOfMemory(); | |
| 216 return -1; | |
| 217 } | |
| 218 if ( video->GetGammaRamp ) { | |
| 219 /* Get the real hardware gamma */ | |
| 220 video->GetGammaRamp(this, video->gamma); | |
| 221 } else { | |
| 222 /* Assume an identity gamma */ | |
| 223 int i; | |
| 224 for ( i=0; i<256; ++i ) { | |
| 225 video->gamma[0*256+i] = (i << 8) | i; | |
| 226 video->gamma[1*256+i] = (i << 8) | i; | |
| 227 video->gamma[2*256+i] = (i << 8) | i; | |
| 228 } | |
| 229 } | |
| 230 } | |
| 231 | |
| 232 /* Just copy from our internal table */ | |
| 233 if ( red ) { | |
| 234 memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); | |
| 235 } | |
| 236 if ( green ) { | |
| 237 memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); | |
| 238 } | |
| 239 if ( blue ) { | |
| 240 memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); | |
| 241 } | |
| 242 return 0; | |
| 243 } |