| 1 | /* |
| 2 | SDL - Simple DirectMedia Layer |
| 3 | Copyright (C) 1997-2009 Sam Lantinga |
| 4 | |
| 5 | This library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 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 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with this library; if not, write to the Free Software |
| 17 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 18 | |
| 19 | Sam Lantinga |
| 20 | slouken@libsdl.org |
| 21 | */ |
| 22 | #include "SDL_config.h" |
| 23 | |
| 24 | /* Gamma correction support */ |
| 25 | |
| 26 | #ifdef HAVE_MATH_H |
| 27 | #include <math.h> /* Used for calculating gamma ramps */ |
| 28 | #else |
| 29 | /* Math routines from uClibc: http://www.uclibc.org */ |
| 30 | #include "math_private.h" |
| 31 | #include "e_sqrt.h" |
| 32 | #include "e_pow.h" |
| 33 | #include "e_log.h" |
| 34 | #define pow(x, y) __ieee754_pow(x, y) |
| 35 | #define log(x) __ieee754_log(x) |
| 36 | #endif |
| 37 | |
| 38 | #include "SDL_sysvideo.h" |
| 39 | |
| 40 | |
| 41 | static void CalculateGammaRamp(float gamma, Uint16 *ramp) |
| 42 | { |
| 43 | int i; |
| 44 | |
| 45 | /* 0.0 gamma is all black */ |
| 46 | if ( gamma <= 0.0f ) { |
| 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 == 1.0f ) { |
| 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 = 0.0f; |
| 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 > 0.0f ) { |
| 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 | |
| 144 | int SDL_SetGammaRamp(const Uint16 *red, const Uint16 *green, const Uint16 *blue) |
| 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 ) { |
| 164 | SDL_memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); |
| 165 | } |
| 166 | if ( green ) { |
| 167 | SDL_memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); |
| 168 | } |
| 169 | if ( blue ) { |
| 170 | SDL_memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); |
| 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 ) { |
| 203 | video->gamma = SDL_malloc(3*256*sizeof(*video->gamma)); |
| 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 ) { |
| 224 | SDL_memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); |
| 225 | } |
| 226 | if ( green ) { |
| 227 | SDL_memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); |
| 228 | } |
| 229 | if ( blue ) { |
| 230 | SDL_memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); |
| 231 | } |
| 232 | return 0; |
| 233 | } |