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1 /* |
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2 SDL - Simple DirectMedia Layer |
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3 Copyright (C) 1997-2006 Sam Lantinga |
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4 |
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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 |
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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. |
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9 |
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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 Lesser General Public License for more details. |
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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 |
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18 |
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19 Sam Lantinga |
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20 slouken@libsdl.org |
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21 */ |
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22 #include "SDL_config.h" |
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23 |
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24 /* Gamma correction support */ |
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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) |
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36 #endif |
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37 |
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38 #include "SDL_sysvideo.h" |
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39 |
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40 |
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41 static void CalculateGammaRamp(float gamma, Uint16 *ramp) |
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42 { |
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43 int i; |
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44 |
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45 /* 0.0 gamma is all black */ |
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46 if ( gamma <= 0.0f ) { |
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47 for ( i=0; i<256; ++i ) { |
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48 ramp[i] = 0; |
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49 } |
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50 return; |
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51 } else |
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52 /* 1.0 gamma is identity */ |
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53 if ( gamma == 1.0f ) { |
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54 for ( i=0; i<256; ++i ) { |
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55 ramp[i] = (i << 8) | i; |
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56 } |
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57 return; |
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58 } else |
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59 /* Calculate a real gamma ramp */ |
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60 { int value; |
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61 gamma = 1.0f / gamma; |
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62 for ( i=0; i<256; ++i ) { |
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63 value = (int)(pow((double)i/256.0, gamma)*65535.0+0.5); |
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64 if ( value > 65535 ) { |
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65 value = 65535; |
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66 } |
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67 ramp[i] = (Uint16)value; |
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68 } |
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69 } |
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70 } |
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71 static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp) |
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72 { |
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73 /* The following is adapted from a post by Garrett Bass on OpenGL |
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74 Gamedev list, March 4, 2000. |
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75 */ |
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76 float sum = 0.0f; |
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77 int i, count = 0; |
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78 |
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79 *gamma = 1.0; |
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80 for ( i = 1; i < 256; ++i ) { |
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81 if ( (ramp[i] != 0) && (ramp[i] != 65535) ) { |
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82 double B = (double)i / 256.0; |
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83 double A = ramp[i] / 65535.0; |
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84 sum += (float) ( log(A) / log(B) ); |
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85 count++; |
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86 } |
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87 } |
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88 if ( count && sum > 0.0f ) { |
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89 *gamma = 1.0f / (sum / count); |
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90 } |
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91 } |
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92 |
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93 int SDL_SetGamma(float red, float green, float blue) |
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94 { |
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95 int succeeded; |
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96 SDL_VideoDevice *video = current_video; |
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97 SDL_VideoDevice *this = current_video; |
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98 |
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99 succeeded = -1; |
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100 /* Prefer using SetGammaRamp(), as it's more flexible */ |
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101 { |
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102 Uint16 ramp[3][256]; |
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103 |
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104 CalculateGammaRamp(red, ramp[0]); |
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105 CalculateGammaRamp(green, ramp[1]); |
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106 CalculateGammaRamp(blue, ramp[2]); |
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107 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); |
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108 } |
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109 if ( (succeeded < 0) && video->SetGamma ) { |
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110 SDL_ClearError(); |
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111 succeeded = video->SetGamma(this, red, green, blue); |
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112 } |
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113 return succeeded; |
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114 } |
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115 |
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116 /* Calculating the gamma by integrating the gamma ramps isn't exact, |
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117 so this function isn't officially supported. |
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118 */ |
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119 int SDL_GetGamma(float *red, float *green, float *blue) |
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120 { |
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121 int succeeded; |
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122 SDL_VideoDevice *video = current_video; |
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123 SDL_VideoDevice *this = current_video; |
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124 |
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125 succeeded = -1; |
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126 /* Prefer using GetGammaRamp(), as it's more flexible */ |
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127 { |
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128 Uint16 ramp[3][256]; |
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129 |
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130 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); |
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131 if ( succeeded >= 0 ) { |
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132 CalculateGammaFromRamp(red, ramp[0]); |
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133 CalculateGammaFromRamp(green, ramp[1]); |
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134 CalculateGammaFromRamp(blue, ramp[2]); |
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135 } |
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136 } |
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137 if ( (succeeded < 0) && video->GetGamma ) { |
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138 SDL_ClearError(); |
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139 succeeded = video->GetGamma(this, red, green, blue); |
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140 } |
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141 return succeeded; |
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142 } |
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143 |
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144 int SDL_SetGammaRamp(const Uint16 *red, const Uint16 *green, const Uint16 *blue) |
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145 { |
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146 int succeeded; |
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147 SDL_VideoDevice *video = current_video; |
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148 SDL_VideoDevice *this = current_video; |
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149 SDL_Surface *screen = SDL_PublicSurface; |
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150 |
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151 /* Verify the screen parameter */ |
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152 if ( !screen ) { |
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153 SDL_SetError("No video mode has been set"); |
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154 return -1; |
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155 } |
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156 |
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157 /* Lazily allocate the gamma tables */ |
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158 if ( ! video->gamma ) { |
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159 SDL_GetGammaRamp(0, 0, 0); |
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160 } |
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161 |
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162 /* Fill the gamma table with the new values */ |
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163 if ( red ) { |
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164 SDL_memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); |
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165 } |
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166 if ( green ) { |
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167 SDL_memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); |
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168 } |
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169 if ( blue ) { |
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170 SDL_memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); |
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171 } |
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172 |
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173 /* Gamma correction always possible on split palettes */ |
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174 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { |
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175 SDL_Palette *pal = screen->format->palette; |
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176 |
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177 /* If physical palette has been set independently, use it */ |
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178 if(video->physpal) |
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179 pal = video->physpal; |
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180 |
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181 SDL_SetPalette(screen, SDL_PHYSPAL, |
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182 pal->colors, 0, pal->ncolors); |
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183 return 0; |
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184 } |
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185 |
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186 /* Try to set the gamma ramp in the driver */ |
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187 succeeded = -1; |
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188 if ( video->SetGammaRamp ) { |
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189 succeeded = video->SetGammaRamp(this, video->gamma); |
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190 } else { |
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191 SDL_SetError("Gamma ramp manipulation not supported"); |
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192 } |
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193 return succeeded; |
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194 } |
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195 |
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196 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) |
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197 { |
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198 SDL_VideoDevice *video = current_video; |
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199 SDL_VideoDevice *this = current_video; |
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200 |
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201 /* Lazily allocate the gamma table */ |
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202 if ( ! video->gamma ) { |
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203 video->gamma = SDL_malloc(3*256*sizeof(*video->gamma)); |
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204 if ( ! video->gamma ) { |
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205 SDL_OutOfMemory(); |
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206 return -1; |
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207 } |
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208 if ( video->GetGammaRamp ) { |
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209 /* Get the real hardware gamma */ |
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210 video->GetGammaRamp(this, video->gamma); |
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211 } else { |
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212 /* Assume an identity gamma */ |
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213 int i; |
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214 for ( i=0; i<256; ++i ) { |
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215 video->gamma[0*256+i] = (i << 8) | i; |
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216 video->gamma[1*256+i] = (i << 8) | i; |
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217 video->gamma[2*256+i] = (i << 8) | i; |
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218 } |
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219 } |
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220 } |
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221 |
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222 /* Just copy from our internal table */ |
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223 if ( red ) { |
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224 SDL_memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); |
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225 } |
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226 if ( green ) { |
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227 SDL_memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); |
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228 } |
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229 if ( blue ) { |
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230 SDL_memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); |
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231 } |
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232 return 0; |
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233 } |