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comparison src/video/SDL_gamma.c @ 0:74212992fb08

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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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children 2cf88672fc7f
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-1:000000000000 0:74212992fb08
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 }