1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
/*********************************************************************
* kd-forest *
* Copyright (C) 2014 Tavian Barnes <tavianator@tavianator.com> *
* *
* This program is free software. It comes without any warranty, to *
* the extent permitted by applicable law. You can redistribute it *
* and/or modify it under the terms of the Do What The Fuck You Want *
* To Public License, Version 2, as published by Sam Hocevar. See *
* the COPYING file or http://www.wtfpl.net/ for more details. *
*********************************************************************/
#include "color.h"
#include <math.h>
#define PI 3.1415926535897932
void
color_unpack(uint8_t pixel[3], uint32_t color)
{
pixel[0] = (color >> 16) & 0xFF;
pixel[1] = (color >> 8) & 0xFF;
pixel[2] = color & 0xFF;
}
void
color_set_RGB(double coords[3], uint32_t color)
{
uint8_t pixel[3];
color_unpack(pixel, color);
for (int i = 0; i < 3; ++i) {
coords[i] = pixel[i]/255.0;
}
}
// Inverse gamma for sRGB
double
sRGB_C_inv(double t)
{
if (t <= 0.040449936) {
return t/12.92;
} else {
return pow((t + 0.055)/1.055, 2.4);
}
}
static void
color_set_XYZ(double XYZ[3], uint32_t color)
{
double RGB[3];
color_set_RGB(RGB, color);
RGB[0] = sRGB_C_inv(RGB[0]);
RGB[1] = sRGB_C_inv(RGB[1]);
RGB[2] = sRGB_C_inv(RGB[2]);
XYZ[0] = 0.4123808838268995*RGB[0] + 0.3575728355732478*RGB[1] + 0.1804522977447919*RGB[2];
XYZ[1] = 0.2126198631048975*RGB[0] + 0.7151387878413206*RGB[1] + 0.0721499433963131*RGB[2];
XYZ[2] = 0.0193434956789248*RGB[0] + 0.1192121694056356*RGB[1] + 0.9505065664127130*RGB[2];
}
// CIE L*a*b* and L*u*v* gamma
static double
Lab_f(double t)
{
if (t > 216.0/24389.0) {
return pow(t, 1.0/3.0);
} else {
return 841.0*t/108.0 + 4.0/29.0;
}
}
// sRGB white point (CIE D50) in XYZ coordinates
static const double WHITE[] = {
[0] = 0.9504060171449392,
[1] = 0.9999085943425312,
[2] = 1.089062231497274,
};
void
color_set_Lab(double coords[3], uint32_t color)
{
double XYZ[3];
color_set_XYZ(XYZ, color);
double fXYZ[] = {
[0] = Lab_f(XYZ[0]/WHITE[0]),
[1] = Lab_f(XYZ[1]/WHITE[1]),
[2] = Lab_f(XYZ[2]/WHITE[2]),
};
coords[0] = 116.0*fXYZ[1] - 16.0;
coords[1] = 500.0*(fXYZ[0] - fXYZ[1]);
coords[2] = 200.0*(fXYZ[1] - fXYZ[2]);
}
void
color_set_Luv(double coords[3], uint32_t color)
{
double XYZ[3];
color_set_XYZ(XYZ, color);
double uv_denom = XYZ[0] + 15.0*XYZ[1] + 3.0*XYZ[2];
if (uv_denom == 0.0) {
coords[0] = 0.0;
coords[1] = 0.0;
coords[2] = 0.0;
return;
}
double white_uv_denom = WHITE[0] + 16.0*WHITE[1] + 3.0*WHITE[2];
double fY = Lab_f(XYZ[1]/WHITE[1]);
double uprime = 4.0*XYZ[0]/uv_denom;
double unprime = 4.0*WHITE[0]/white_uv_denom;
double vprime = 9.0*XYZ[1]/uv_denom;
double vnprime = 9.0*WHITE[1]/white_uv_denom;
coords[0] = 116.0*fY - 16.0;
coords[1] = 13.0*coords[0]*(uprime - unprime);
coords[2] = 13.0*coords[0]*(vprime - vnprime);
}
static double
hue(uint32_t color)
{
double RGB[3];
color_set_RGB(RGB, color);
double hue = atan2(sqrt(3.0)*(RGB[1] - RGB[2]), 2*RGB[0] - RGB[1] - RGB[2]);
if (hue < 0.0) {
hue += 2.0*PI;
}
return hue;
}
int
color_comparator(const void *a, const void *b)
{
double ahue = hue(*(uint32_t *)a);
double bhue = hue(*(uint32_t *)b);
return (ahue > bhue) - (ahue < bhue);
}
|
