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 * - http://www.tecgraf.puc-rio.br/~mgattass/color/ColorIndex.html
14 * - fix theoretical problems with rounding errors in srgb_to_luv_pixel()
15 * - SIMD should help to speed up conversion of large arrays
16 * - maybe try to generate a long switch in color_conv_pixel()
17 * with optimized entries instead of access to interpolation table
18 * - most of multiplications in srgb_to_luv_pixels can be replaced
19 * with tables lookup... tests shows almost the same speed for random
20 * input and cca 40% gain when input colors fit in CPU chache
23 #ifndef _IMAGES_COLOR_H
24 #define _IMAGES_COLOR_H
26 #include "images/images.h"
29 rgb_to_gray_func(uns r, uns g, uns b)
31 return (r * 19660 + g * 38666 + b * 7210) >> 16;
34 extern struct color color_black, color_white;
37 color_make_gray(struct color *color, uns gray)
40 color->color_space = COLOR_SPACE_GRAYSCALE;
44 color_make_rgb(struct color *color, uns r, uns g, uns b)
49 color->color_space = COLOR_SPACE_RGB;
52 void color_put_color_space(byte *dest, struct color *color, enum color_space color_space);
53 void color_put_grayscale(byte *dest, struct color *color);
54 void color_put_rgb(byte *dest, struct color *color);
56 /* Exact slow conversion routines */
57 void srgb_to_xyz_slow(double dest[3], double src[3]);
58 void xyz_to_srgb_slow(double dest[3], double src[3]);
59 void xyz_to_luv_slow(double dest[3], double src[3]);
60 void luv_to_xyz_slow(double dest[3], double src[3]);
63 #define REF_WHITE_X 0.96422
64 #define REF_WHITE_Y 1.
65 #define REF_WHITE_Z 0.82521
67 /* sRGB -> XYZ matrix */
68 #define SRGB_XYZ_XR 0.412424
69 #define SRGB_XYZ_XG 0.357579
70 #define SRGB_XYZ_XB 0.180464
71 #define SRGB_XYZ_YR 0.212656
72 #define SRGB_XYZ_YG 0.715158
73 #define SRGB_XYZ_YB 0.072186
74 #define SRGB_XYZ_ZR 0.019332
75 #define SRGB_XYZ_ZG 0.119193
76 #define SRGB_XYZ_ZB 0.950444
79 /*********************** OPTIMIZED CONVERSION ROUTINES **********************/
81 /* sRGB -> Luv parameters */
82 #define SRGB_TO_LUV_TAB2_SIZE 9
83 #define SRGB_TO_LUV_TAB2_SCALE 11
84 #define SRGB_TO_LUV_TAB3_SIZE 8
85 #define SRGB_TO_LUV_TAB3_SCALE (39 - SRGB_TO_LUV_TAB2_SCALE - SRGB_TO_LUV_TAB3_SIZE)
87 extern u16 srgb_to_luv_tab1[256];
88 extern u16 srgb_to_luv_tab2[9 << SRGB_TO_LUV_TAB2_SIZE];
89 extern u32 srgb_to_luv_tab3[20 << SRGB_TO_LUV_TAB3_SIZE];
91 void srgb_to_luv_init(void);
92 void srgb_to_luv_pixels(byte *dest, byte *src, uns count);
94 /* L covers the interval [0..255]; u and v are centered to 128 and scaled by 1/4 in respect of L */
96 srgb_to_luv_pixel(byte *dest, byte *src)
98 uns r = srgb_to_luv_tab1[src[0]];
99 uns g = srgb_to_luv_tab1[src[1]];
100 uns b = srgb_to_luv_tab1[src[2]];
102 (uns)(4 * SRGB_XYZ_XR * 0xffff) * r +
103 (uns)(4 * SRGB_XYZ_XG * 0xffff) * g +
104 (uns)(4 * SRGB_XYZ_XB * 0xffff) * b;
106 (uns)(9 * SRGB_XYZ_YR * 0xffff) * r +
107 (uns)(9 * SRGB_XYZ_YG * 0xffff) * g +
108 (uns)(9 * SRGB_XYZ_YB * 0xffff) * b;
109 uns l = srgb_to_luv_tab2[y >> (28 - SRGB_TO_LUV_TAB2_SIZE)];
110 dest[0] = l >> (SRGB_TO_LUV_TAB2_SCALE - 8);
112 (uns)((SRGB_XYZ_XR + 15 * SRGB_XYZ_YR + 3 * SRGB_XYZ_ZR) * 0x7fff) * r +
113 (uns)((SRGB_XYZ_XG + 15 * SRGB_XYZ_YG + 3 * SRGB_XYZ_ZG) * 0x7fff) * g +
114 (uns)((SRGB_XYZ_XB + 15 * SRGB_XYZ_YB + 3 * SRGB_XYZ_ZB) * 0x7fff) * b;
115 uns s = srgb_to_luv_tab3[sum >> (27 - SRGB_TO_LUV_TAB3_SIZE)];
116 int xs = ((u64)x * s) >> 32;
117 int ys = ((u64)y * s) >> 32;
118 int xw = ((4 * 13) << (SRGB_TO_LUV_TAB3_SCALE - 4)) *
119 REF_WHITE_X / (REF_WHITE_X + 15 * REF_WHITE_Y + 3 * REF_WHITE_Z);
120 int yw = ((9 * 13) << (SRGB_TO_LUV_TAB3_SCALE - 4)) *
121 REF_WHITE_Y / (REF_WHITE_X + 15 * REF_WHITE_Y + 3 * REF_WHITE_Z);
122 int u = (int)(l) * (xs - xw);
123 int v = (int)(l) * (ys - yw);
124 dest[1] = 128 + (u >> (SRGB_TO_LUV_TAB3_SCALE + SRGB_TO_LUV_TAB2_SCALE - 10));
125 dest[2] = 128 + (v >> (SRGB_TO_LUV_TAB3_SCALE + SRGB_TO_LUV_TAB2_SCALE - 10));
129 /****************** GENERAL INTERPOLATION IN 3D GRID ********************/
131 #define COLOR_CONV_SIZE 5 /* 128K conversion grid size */
132 #define COLOR_CONV_OFS 3 /* 8K interpolation table size */
134 struct color_grid_node {
138 struct color_interpolation_node {
143 extern struct color_grid_node *srgb_to_luv_grid;
144 extern struct color_interpolation_node *color_interpolation_table;
146 void color_conv_init(void);
147 void color_conv_pixels(byte *dest, byte *src, uns count, struct color_grid_node *grid);
149 #define COLOR_CONV_SCALE_CONST (((((1 << COLOR_CONV_SIZE) - 1) << 16) + (1 << (16 - COLOR_CONV_OFS))) / 255)
152 color_conv_pixel(byte *dest, byte *src, struct color_grid_node *grid)
154 uns s0 = src[0] * COLOR_CONV_SCALE_CONST;
155 uns s1 = src[1] * COLOR_CONV_SCALE_CONST;
156 uns s2 = src[2] * COLOR_CONV_SCALE_CONST;
157 struct color_grid_node *g0, *g1, *g2, *g3, *g = grid +
158 ((s0 >> 16) + ((s1 >> 16) << COLOR_CONV_SIZE) + ((s2 >> 16) << (2 * COLOR_CONV_SIZE)));
159 struct color_interpolation_node *n = color_interpolation_table +
160 (((s0 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - COLOR_CONV_OFS)) +
161 ((s1 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - 2 * COLOR_CONV_OFS)) +
162 ((s2 & (0x10000 - (0x10000 >> COLOR_CONV_OFS))) >> (16 - 3 * COLOR_CONV_OFS)));
167 dest[0] = (g0->val[0] * n->mul[0] + g1->val[0] * n->mul[1] +
168 g2->val[0] * n->mul[2] + g3->val[0] * n->mul[3] + 128) >> 8;
169 dest[1] = (g0->val[1] * n->mul[0] + g1->val[1] * n->mul[1] +
170 g2->val[1] * n->mul[2] + g3->val[1] * n->mul[3] + 128) >> 8;
171 dest[2] = (g0->val[2] * n->mul[0] + g1->val[2] * n->mul[1] +
172 g2->val[2] * n->mul[2] + g3->val[2] * n->mul[3] + 128) >> 8;