Mercurial > sdl-ios-xcode
comparison src/video/SDL_gamma.c @ 0:74212992fb08
Initial revision
author | Sam Lantinga <slouken@lokigames.com> |
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date | Thu, 26 Apr 2001 16:45:43 +0000 |
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children | 2cf88672fc7f |
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-1:000000000000 | 0:74212992fb08 |
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1 /* | |
2 SDL - Simple DirectMedia Layer | |
3 Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga | |
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 | |
20 slouken@devolution.com | |
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> | |
36 | |
37 #include "SDL_error.h" | |
38 #include "SDL_sysvideo.h" | |
39 | |
40 #ifdef USE_MATH_H | |
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 #endif /* USE_MATH_H */ | |
93 | |
94 int SDL_SetGamma(float red, float green, float blue) | |
95 { | |
96 int succeeded; | |
97 SDL_VideoDevice *video = current_video; | |
98 SDL_VideoDevice *this = current_video; | |
99 | |
100 succeeded = -1; | |
101 #ifdef USE_MATH_H | |
102 /* Prefer using SetGammaRamp(), as it's more flexible */ | |
103 { | |
104 Uint16 ramp[3][256]; | |
105 | |
106 CalculateGammaRamp(red, ramp[0]); | |
107 CalculateGammaRamp(green, ramp[1]); | |
108 CalculateGammaRamp(blue, ramp[2]); | |
109 succeeded = SDL_SetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
110 } | |
111 #else | |
112 SDL_SetError("Gamma correction not supported"); | |
113 #endif | |
114 if ( (succeeded < 0) && video->SetGamma ) { | |
115 SDL_ClearError(); | |
116 succeeded = video->SetGamma(this, red, green, blue); | |
117 } | |
118 return succeeded; | |
119 } | |
120 | |
121 /* Calculating the gamma by integrating the gamma ramps isn't exact, | |
122 so this function isn't officially supported. | |
123 */ | |
124 int SDL_GetGamma(float *red, float *green, float *blue) | |
125 { | |
126 int succeeded; | |
127 SDL_VideoDevice *video = current_video; | |
128 SDL_VideoDevice *this = current_video; | |
129 | |
130 succeeded = -1; | |
131 #ifdef USE_MATH_H | |
132 /* Prefer using GetGammaRamp(), as it's more flexible */ | |
133 { | |
134 Uint16 ramp[3][256]; | |
135 | |
136 succeeded = SDL_GetGammaRamp(ramp[0], ramp[1], ramp[2]); | |
137 if ( succeeded >= 0 ) { | |
138 CalculateGammaFromRamp(red, ramp[0]); | |
139 CalculateGammaFromRamp(green, ramp[1]); | |
140 CalculateGammaFromRamp(blue, ramp[2]); | |
141 } | |
142 } | |
143 #else | |
144 SDL_SetError("Gamma correction not supported"); | |
145 #endif | |
146 if ( (succeeded < 0) && video->GetGamma ) { | |
147 SDL_ClearError(); | |
148 succeeded = video->GetGamma(this, red, green, blue); | |
149 } | |
150 return succeeded; | |
151 } | |
152 | |
153 int SDL_SetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
154 { | |
155 int succeeded; | |
156 SDL_VideoDevice *video = current_video; | |
157 SDL_VideoDevice *this = current_video; | |
158 SDL_Surface *screen = SDL_PublicSurface; | |
159 | |
160 /* Verify the screen parameter */ | |
161 if ( !screen ) { | |
162 SDL_SetError("No video mode has been set"); | |
163 return -1; | |
164 } | |
165 | |
166 /* Lazily allocate the gamma tables */ | |
167 if ( ! video->gamma ) { | |
168 SDL_GetGammaRamp(0, 0, 0); | |
169 } | |
170 | |
171 /* Fill the gamma table with the new values */ | |
172 if ( red ) { | |
173 memcpy(&video->gamma[0*256], red, 256*sizeof(*video->gamma)); | |
174 } | |
175 if ( green ) { | |
176 memcpy(&video->gamma[1*256], green, 256*sizeof(*video->gamma)); | |
177 } | |
178 if ( blue ) { | |
179 memcpy(&video->gamma[2*256], blue, 256*sizeof(*video->gamma)); | |
180 } | |
181 | |
182 /* Gamma correction always possible on split palettes */ | |
183 if ( (screen->flags & SDL_HWPALETTE) == SDL_HWPALETTE ) { | |
184 SDL_Palette *pal = screen->format->palette; | |
185 | |
186 /* If physical palette has been set independently, use it */ | |
187 if(video->physpal) | |
188 pal = video->physpal; | |
189 | |
190 SDL_SetPalette(screen, SDL_PHYSPAL, | |
191 pal->colors, 0, pal->ncolors); | |
192 return 0; | |
193 } | |
194 | |
195 /* Try to set the gamma ramp in the driver */ | |
196 succeeded = -1; | |
197 if ( video->SetGammaRamp ) { | |
198 succeeded = video->SetGammaRamp(this, video->gamma); | |
199 } else { | |
200 SDL_SetError("Gamma ramp manipulation not supported"); | |
201 } | |
202 return succeeded; | |
203 } | |
204 | |
205 int SDL_GetGammaRamp(Uint16 *red, Uint16 *green, Uint16 *blue) | |
206 { | |
207 SDL_VideoDevice *video = current_video; | |
208 SDL_VideoDevice *this = current_video; | |
209 | |
210 /* Lazily allocate the gamma table */ | |
211 if ( ! video->gamma ) { | |
212 video->gamma = malloc(3*256*sizeof(*video->gamma)); | |
213 if ( ! video->gamma ) { | |
214 SDL_OutOfMemory(); | |
215 return -1; | |
216 } | |
217 if ( video->GetGammaRamp ) { | |
218 /* Get the real hardware gamma */ | |
219 video->GetGammaRamp(this, video->gamma); | |
220 } else { | |
221 /* Assume an identity gamma */ | |
222 int i; | |
223 for ( i=0; i<256; ++i ) { | |
224 video->gamma[0*256+i] = (i << 8) | i; | |
225 video->gamma[1*256+i] = (i << 8) | i; | |
226 video->gamma[2*256+i] = (i << 8) | i; | |
227 } | |
228 } | |
229 } | |
230 | |
231 /* Just copy from our internal table */ | |
232 if ( red ) { | |
233 memcpy(red, &video->gamma[0*256], 256*sizeof(*red)); | |
234 } | |
235 if ( green ) { | |
236 memcpy(green, &video->gamma[1*256], 256*sizeof(*green)); | |
237 } | |
238 if ( blue ) { | |
239 memcpy(blue, &video->gamma[2*256], 256*sizeof(*blue)); | |
240 } | |
241 return 0; | |
242 } |