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
|
/*********************************************************************
* 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>
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);
}
|
