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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997, 1998, 1999, 2000, 2001 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 Library General Public
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7 License as published by the Free Software Foundation; either
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8 version 2 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 Library 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 Library General Public
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16 License along with this library; if not, write to the Free
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17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18
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19 Sam Lantinga
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20 slouken@devolution.com
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21 */
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22
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23 #ifdef SAVE_RCSID
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24 static char rcsid =
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25 "@(#) $Id$";
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26 #endif
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27
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28 /* Gamma correction support */
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29
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30 #define USE_MATH_H /* Used for calculating gamma ramps */
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31
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32 #ifdef USE_MATH_H
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33 #include <math.h>
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34 #endif
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35 #include <stdlib.h>
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152
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36 #include <string.h>
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0
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37
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38 #include "SDL_error.h"
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39 #include "SDL_sysvideo.h"
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40
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41 #ifdef USE_MATH_H
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42 static void CalculateGammaRamp(float gamma, Uint16 *ramp)
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43 {
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44 int i;
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45
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46 /* 0.0 gamma is all black */
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47 if ( gamma <= 0.0 ) {
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48 for ( i=0; i<256; ++i ) {
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49 ramp[i] = 0;
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50 }
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51 return;
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52 } else
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53 /* 1.0 gamma is identity */
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54 if ( gamma == 1.0 ) {
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55 for ( i=0; i<256; ++i ) {
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56 ramp[i] = (i << 8) | i;
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57 }
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58 return;
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59 } else
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60 /* Calculate a real gamma ramp */
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61 { int value;
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62 gamma = 1.0f / gamma;
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63 for ( i=0; i<256; ++i ) {
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64 value = (int)(pow((double)i/256.0, gamma)*65535.0+0.5);
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65 if ( value > 65535 ) {
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66 value = 65535;
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67 }
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68 ramp[i] = (Uint16)value;
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69 }
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70 }
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71 }
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72 static void CalculateGammaFromRamp(float *gamma, Uint16 *ramp)
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73 {
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74 /* The following is adapted from a post by Garrett Bass on OpenGL
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75 Gamedev list, March 4, 2000.
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76 */
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77 float sum = 0.0;
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78 int i, count = 0;
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79
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80 *gamma = 1.0;
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81 for ( i = 1; i < 256; ++i ) {
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82 if ( (ramp[i] != 0) && (ramp[i] != 65535) ) {
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83 double B = (double)i / 256.0;
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84 double A = ramp[i] / 65535.0;
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85 sum += (float) ( log(A) / log(B) );
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86 count++;
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87 }
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88 }
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89 if ( count && sum ) {
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90 *gamma = 1.0f / (sum / count);
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91 }
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92 }
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93 #endif /* USE_MATH_H */
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94
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95 int SDL_SetGamma(float red, float green, float blue)
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96 {
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97 int succeeded;
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98 SDL_VideoDevice *video = current_video;
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99 SDL_VideoDevice *this = current_video;
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100
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101 succeeded = -1;
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102 #ifdef USE_MATH_H
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103 /* Prefer using SetGammaRamp(), as it's more flexible */
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104 {
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105 Uint16 ramp[3][256];
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106
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107 CalculateGammaRamp(red, ramp[0]);
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108 CalculateGammaRamp(green, ramp[1]);
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109 CalculateGammaRamp(blue, ramp[2]);
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110 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]);
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111 }
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112 #else
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113 SDL_SetError("Gamma correction not supported");
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114 #endif
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115 if ( (succeeded < 0) && video->SetGamma ) {
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116 SDL_ClearError();
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117 succeeded = video->SetGamma(this, red, green, blue);
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118 }
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119 return succeeded;
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120 }
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121
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122 /* Calculating the gamma by integrating the gamma ramps isn't exact,
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123 so this function isn't officially supported.
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124 */
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125 int SDL_GetGamma(float *red, float *green, float *blue)
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126 {
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127 int succeeded;
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128 SDL_VideoDevice *video = current_video;
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129 SDL_VideoDevice *this = current_video;
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130
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131 succeeded = -1;
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132 #ifdef USE_MATH_H
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133 /* Prefer using GetGammaRamp(), as it's more flexible */
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134 {
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135 Uint16 ramp[3][256];
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136
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137 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]);
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138 if ( succeeded >= 0 ) {
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139 CalculateGammaFromRamp(red, ramp[0]);
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140 CalculateGammaFromRamp(green, ramp[1]);
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141 CalculateGammaFromRamp(blue, ramp[2]);
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142 }
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143 }
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144 #else
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145 SDL_SetError("Gamma correction not supported");
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146 #endif
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147 if ( (succeeded < 0) && video->GetGamma ) {
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148 SDL_ClearError();
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149 succeeded = video->GetGamma(this, red, green, blue);
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150 }
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151 return succeeded;
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152 }
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153
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154 int SDL_SetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue)
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155 {
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156 int succeeded;
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157 SDL_VideoDevice *video = current_video;
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158 SDL_VideoDevice *this = current_video;
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159 SDL_Surface *screen = SDL_PublicSurface;
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160
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161 /* Verify the screen parameter */
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162 if ( !screen ) {
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163 SDL_SetError("No video mode has been set");
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164 return -1;
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165 }
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166
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167 /* Lazily allocate the gamma tables */
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168 if ( ! video->gamma ) {
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169 SDL_GetGammaRamp(0, 0, 0);
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170 }
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171
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172 /* Fill the gamma table with the new values */
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173 if ( red ) {
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174 memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma));
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175 }
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176 if ( green ) {
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177 memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma));
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178 }
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179 if ( blue ) {
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180 memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma));
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181 }
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182
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183 /* Gamma correction always possible on split palettes */
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184 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) {
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185 SDL_Palette *pal = screen->format->palette;
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186
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187 /* If physical palette has been set independently, use it */
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188 if(video->physpal)
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189 pal = video->physpal;
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190
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191 SDL_SetPalette(screen, SDL_PHYSPAL,
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192 pal->colors, 0, pal->ncolors);
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193 return 0;
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194 }
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195
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196 /* Try to set the gamma ramp in the driver */
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197 succeeded = -1;
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198 if ( video->SetGammaRamp ) {
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199 succeeded = video->SetGammaRamp(this, video->gamma);
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200 } else {
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201 SDL_SetError("Gamma ramp manipulation not supported");
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202 }
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203 return succeeded;
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204 }
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205
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206 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue)
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207 {
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208 SDL_VideoDevice *video = current_video;
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209 SDL_VideoDevice *this = current_video;
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210
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211 /* Lazily allocate the gamma table */
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212 if ( ! video->gamma ) {
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213 video->gamma = malloc(3*256*sizeof(*video->gamma));
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214 if ( ! video->gamma ) {
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215 SDL_OutOfMemory();
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216 return -1;
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217 }
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218 if ( video->GetGammaRamp ) {
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219 /* Get the real hardware gamma */
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220 video->GetGammaRamp(this, video->gamma);
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221 } else {
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222 /* Assume an identity gamma */
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223 int i;
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224 for ( i=0; i<256; ++i ) {
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225 video->gamma[0*256+i] = (i << 8) | i;
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226 video->gamma[1*256+i] = (i << 8) | i;
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227 video->gamma[2*256+i] = (i << 8) | i;
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228 }
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229 }
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230 }
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231
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232 /* Just copy from our internal table */
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233 if ( red ) {
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234 memcpy(red, &video->gamma[0*256], 256*sizeof(*red));
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235 }
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236 if ( green ) {
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237 memcpy(green, &video->gamma[1*256], 256*sizeof(*green));
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238 }
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239 if ( blue ) {
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240 memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue));
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241 }
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242 return 0;
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243 }
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