2 * Image Library -- Color Spaces
4 * (c) 2006 Pavel Charvat <pchar@ucw.cz>
6 * This software may be freely distributed and used according to the terms
7 * of the GNU Lesser General Public License.
11 * - A Review of RGB Color Spaces, Danny Pascale (2003)
12 * - http://www.adobe.com/digitalimag/pdfs/AdobeRGB1998.pdf
13 * - http://www.tecgraf.puc-rio.br/~mgattass/color/ColorIndex.html
16 * - fix theoretical problems with rounding errors in srgb_to_luv_pixel()
17 * - SIMD should help to speed up conversion of large arrays
18 * - maybe try to generate a long switch in color_conv_pixel()
19 * with optimized entries instead of access to interpolation table
20 * - most of multiplications in srgb_to_luv_pixels can be replaced
21 * with tables lookup... tests shows almost the same speed for random
22 * input and cca 40% gain when input colors fit in CPU chache
25 #ifndef _IMAGES_COLOR_H
26 #define _IMAGES_COLOR_H
28 #include "images/images.h"
30 /* Basic color spaces */
32 COLOR_SPACE_UNKNOWN = 0,
33 COLOR_SPACE_UNKNOWN_1 = 1, /* unknown 1-channel color space */
34 COLOR_SPACE_UNKNOWN_2 = 2, /* unknown 2-channels color space */
35 COLOR_SPACE_UNKNOWN_3 = 3, /* unknown 3-channels color space */
36 COLOR_SPACE_UNKNOWN_4 = 4, /* unknown 4-channels color space */
37 COLOR_SPACE_UNKNOWN_MAX = 4,
38 COLOR_SPACE_GRAYSCALE,
49 extern uns color_space_channels[COLOR_SPACE_MAX];
50 extern byte *color_space_name[COLOR_SPACE_MAX];
52 /* Color space ID <-> name conversions */
53 byte *color_space_id_to_name(uns id);
54 uns color_space_name_to_id(byte *name);
56 /* Struct color manipulation */
57 int color_get(struct color *color, byte *src, uns src_space);
58 int color_put(struct image_context *ctx, struct color *color, byte *dest, uns dest_space);
61 color_make_gray(struct color *color, uns gray)
64 color->color_space = COLOR_SPACE_GRAYSCALE;
68 color_make_rgb(struct color *color, uns r, uns g, uns b)
73 color->color_space = COLOR_SPACE_RGB;
76 extern struct color color_black, color_white;
78 /* Conversion between various pixel formats */
81 IMAGE_CONV_FILL_ALPHA = 1,
82 IMAGE_CONV_COPY_ALPHA = 2,
83 IMAGE_CONV_APPLY_ALPHA = 4,
86 struct image_conv_options {
88 struct color background;
91 extern struct image_conv_options image_conv_defaults;
93 int image_conv(struct image_context *ctx, struct image *dest, struct image *src, struct image_conv_options *opt);
95 /* Color spaces in the CIE 1931 chromacity diagram */
97 struct color_space_chromacity_info {
104 struct color_space_gamma_info {
106 double detailed_gamma;
112 struct color_space_info {
114 struct color_space_chromacity_info chromacity;
115 struct color_space_gamma_info gamma;
119 color_illuminant_d50[2],
120 color_illuminant_d65[2],
121 color_illuminant_e[2];
123 extern const struct color_space_info
124 color_adobe_rgb_info, /* Adobe RGB (1998) */
125 color_apple_rgb_info, /* Apple RGB */
126 color_cie_rgb_info, /* CIE RGB */
127 color_color_match_rgb_info, /* ColorMatch RGB */
128 color_srgb_info; /* sRGB */
130 /* These routines do not check numeric errors! */
131 void color_compute_color_space_to_xyz_matrix(double matrix[9], const struct color_space_chromacity_info *space);
132 void color_compute_bradford_matrix(double matrix[9], const double src[2], const double dest[2]);
133 void color_compute_color_spaces_conversion_matrix(double matrix[9], const struct color_space_chromacity_info *src, const struct color_space_chromacity_info *dest);
134 void color_invert_matrix(double dest[9], double matrix[9]);
137 rgb_to_gray_func(uns r, uns g, uns b)
139 return (r * 19660 + g * 38666 + b * 7210) >> 16;
142 /* Exact slow conversion routines */
143 void srgb_to_xyz_exact(double dest[3], double src[3]);
144 void xyz_to_srgb_exact(double dest[3], double src[3]);
145 void xyz_to_luv_exact(double dest[3], double src[3]);
146 void luv_to_xyz_exact(double dest[3], double src[3]);
147 void rgb_to_cmyk_exact(double dest[4], double src[3]);
148 void cmyk_to_rgb_exact(double dest[3], double src[4]);
150 /* Reference white */
151 #define REF_WHITE_X 0.96422
152 #define REF_WHITE_Y 1.
153 #define REF_WHITE_Z 0.82521
155 /* sRGB -> XYZ matrix */
156 #define SRGB_XYZ_XR 0.412424
157 #define SRGB_XYZ_XG 0.357579
158 #define SRGB_XYZ_XB 0.180464
159 #define SRGB_XYZ_YR 0.212656
160 #define SRGB_XYZ_YG 0.715158
161 #define SRGB_XYZ_YB 0.072186
162 #define SRGB_XYZ_ZR 0.019332
163 #define SRGB_XYZ_ZG 0.119193
164 #define SRGB_XYZ_ZB 0.950444
167 /*********************** OPTIMIZED CONVERSION ROUTINES **********************/
169 /* sRGB -> Luv parameters */
170 #define SRGB_TO_LUV_TAB2_SIZE 9
171 #define SRGB_TO_LUV_TAB2_SCALE 11
172 #define SRGB_TO_LUV_TAB3_SIZE 8
173 #define SRGB_TO_LUV_TAB3_SCALE (39 - SRGB_TO_LUV_TAB2_SCALE - SRGB_TO_LUV_TAB3_SIZE)
175 extern u16 srgb_to_luv_tab1[256];
176 extern u16 srgb_to_luv_tab2[9 << SRGB_TO_LUV_TAB2_SIZE];
177 extern u32 srgb_to_luv_tab3[20 << SRGB_TO_LUV_TAB3_SIZE];
179 void srgb_to_luv_init(void);
180 void srgb_to_luv_pixels(byte *dest, byte *src, uns count);
182 /* L covers the interval [0..255]; u and v are centered to 128 and scaled by 1/4 in respect of L */
184 srgb_to_luv_pixel(byte *dest, byte *src)
186 uns r = srgb_to_luv_tab1[src[0]];
187 uns g = srgb_to_luv_tab1[src[1]];
188 uns b = srgb_to_luv_tab1[src[2]];
190 (uns)(4 * SRGB_XYZ_XR * 0xffff) * r +
191 (uns)(4 * SRGB_XYZ_XG * 0xffff) * g +
192 (uns)(4 * SRGB_XYZ_XB * 0xffff) * b;
194 (uns)(9 * SRGB_XYZ_YR * 0xffff) * r +
195 (uns)(9 * SRGB_XYZ_YG * 0xffff) * g +
196 (uns)(9 * SRGB_XYZ_YB * 0xffff) * b;
197 uns l = srgb_to_luv_tab2[y >> (28 - SRGB_TO_LUV_TAB2_SIZE)];
198 dest[0] = l >> (SRGB_TO_LUV_TAB2_SCALE - 8);
200 (uns)((SRGB_XYZ_XR + 15 * SRGB_XYZ_YR + 3 * SRGB_XYZ_ZR) * 0x7fff) * r +
201 (uns)((SRGB_XYZ_XG + 15 * SRGB_XYZ_YG + 3 * SRGB_XYZ_ZG) * 0x7fff) * g +
202 (uns)((SRGB_XYZ_XB + 15 * SRGB_XYZ_YB + 3 * SRGB_XYZ_ZB) * 0x7fff) * b;
203 uns s = srgb_to_luv_tab3[sum >> (27 - SRGB_TO_LUV_TAB3_SIZE)];
204 int xs = ((u64)x * s) >> 32;
205 int ys = ((u64)y * s) >> 32;
206 int xw = ((4 * 13) << (SRGB_TO_LUV_TAB3_SCALE - 4)) *
207 REF_WHITE_X / (REF_WHITE_X + 15 * REF_WHITE_Y + 3 * REF_WHITE_Z);
208 int yw = ((9 * 13) << (SRGB_TO_LUV_TAB3_SCALE - 4)) *
209 REF_WHITE_Y / (REF_WHITE_X + 15 * REF_WHITE_Y + 3 * REF_WHITE_Z);
210 int u = (int)(l) * (xs - xw);
211 int v = (int)(l) * (ys - yw);
212 dest[1] = 128 + (u >> (SRGB_TO_LUV_TAB3_SCALE + SRGB_TO_LUV_TAB2_SCALE - 10));
213 dest[2] = 128 + (v >> (SRGB_TO_LUV_TAB3_SCALE + SRGB_TO_LUV_TAB2_SCALE - 10));
217 /****************** GENERAL INTERPOLATION IN 3D GRID ********************/
219 #define COLOR_CONV_SIZE 5 /* 128K conversion grid size */
220 #define COLOR_CONV_OFS 3 /* 8K interpolation table size */
222 struct color_grid_node {
226 struct color_interpolation_node {
231 extern struct color_grid_node *srgb_to_luv_grid;
232 extern struct color_interpolation_node *color_interpolation_table;
234 void color_conv_init(void);
235 void color_conv_pixels(byte *dest, byte *src, uns count, struct color_grid_node *grid);
237 #define COLOR_CONV_SCALE_CONST (((((1 << COLOR_CONV_SIZE) - 1) << 16) + (1 << (16 - COLOR_CONV_OFS))) / 255)
240 color_conv_pixel(byte *dest, byte *src, struct color_grid_node *grid)
242 uns s0 = src[0] * COLOR_CONV_SCALE_CONST;
243 uns s1 = src[1] * COLOR_CONV_SCALE_CONST;
244 uns s2 = src[2] * COLOR_CONV_SCALE_CONST;
245 struct color_grid_node *g0, *g1, *g2, *g3, *g = grid +
246 ((s0 >> 16) + ((s1 >> 16) << COLOR_CONV_SIZE) + ((s2 >> 16) << (2 * COLOR_CONV_SIZE)));
247 struct color_interpolation_node *n = color_interpolation_table +
248 (((s0 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - COLOR_CONV_OFS)) +
249 ((s1 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - 2 * COLOR_CONV_OFS)) +
250 ((s2 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - 3 * COLOR_CONV_OFS)));
255 dest[0] = (g0->val[0] * n->mul[0] + g1->val[0] * n->mul[1] +
256 g2->val[0] * n->mul[2] + g3->val[0] * n->mul[3] + 128) >> 8;
257 dest[1] = (g0->val[1] * n->mul[0] + g1->val[1] * n->mul[1] +
258 g2->val[1] * n->mul[2] + g3->val[1] * n->mul[3] + 128) >> 8;
259 dest[2] = (g0->val[2] * n->mul[0] + g1->val[2] * n->mul[1] +
260 g2->val[2] * n->mul[2] + g3->val[2] * n->mul[3] + 128) >> 8;