e14743d1 |
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 | } |