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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
#!/usr/bin/env python3
# Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
def linear_to_standard(*colour):
'''
Convert [0, 1] linear RGB to [0, 1] sRGB
@param colour:*float The red component, the green component, and the blue component
@return :[float, float, float] The red, green and blue components
'''
return [12.92 * c if c <= 0.0031308 else (1 + 0.055) * c ** (1 / 2.4) - 0.055 for c in colour]
def standard_to_linear(*colour):
'''
Convert [0, 1] sRGB to [0, 1] linear RGB
@param colour:*float The red component, the green component, and the blue component
@return :[float, float, float] The red, green and blue components
'''
return [c / 12.92 if c <= 0.04045 else ((c + 0.055) / (1 + 0.055)) ** 2.4 for c in colour]
def ciexyy_to_ciexyz(x, y, Y):
'''
Convert CIE xyY to CIE XYZ
@param x:float The x parameter
@param y:float The y parameter
@param Y:float The Y parameter
@return :[float, float, float] The X, Y and Z parameters
'''
return [Y if y == 0 else Y * x / y, Y, Y if y == 0 else Y * (1 - x - y) / y]
def ciexyz_to_ciexyy(X, Y, Z):
'''
Convert CIE XYZ to CIE xyY
@param X:float The X parameter
@param Y:float The Y parameter
@param Z:float The Z parameter
@return :[float, float, float] The x, y and Y parameters
'''
if X + Y + Z == 0:
return [0, 0, 0]
y = Y / (X + Y + Z)
x = X / (X + Y + Z)
return [x, y, Y]
def matrix_mul_vector(matrix, vector):
'''
Multiplies a matrix with a vector
@param matrix:list<list<int>> The matrix
@param vector:list<int> The vector
@return :list<int> The resulting vector
'''
return [[r * v for r, v in zip(row, vector)] for row in matrix]
ciexyz_to_linear_matrix = [[ 3.240450, -1.537140, -0.4985320],
[-0.969266, 1.876010, 0.0415561],
[0.0556434, -0.204026, 1.0572300]]
def ciexyz_to_linear(X, Y, Z):
'''
Convert CIE XYZ to [0, 1] linear RGB
@param X:float The X parameter
@param Y:float The Y parameter
@param Z:float The Z parameter
@return :[float, float, float] The red, green and blue components
'''
return matrix_mul_vector(ciexyz_to_linear_matrix, [X, Y, Z])
linear_to_ciexyz_matrix = [[0.4124564, 0.3575761, 0.1804375],
[0.2126729, 0.7151522, 0.0721750],
[0.0193339, 0.1191920, 0.9503041]]
def linear_to_ciexyz(r, g, b):
'''
Convert [0, 1] linear RGB to CIE XYZ
@param r:float The red component
@param g:float The green component
@param b:float The blue component
@return :[float, float, float] The X, Y and Z parameters
'''
return matrix_mul_vector(linear_to_ciexyz_matrix, [r, g, b])
def srgb_to_ciexyy(r, g, b):
'''
Convert [0, 1] sRGB to CIE xyY
@param r:float The red component
@param g:float The green component
@param b:float The blue component
@return :[float, float, float] The x, y and Y parameters
'''
if r == g == b == 0:
return (0.312857, 0.328993, 0)
rc = standard_to_linear(r, g, b)
rc = linear_to_ciexyz(*rc)
rc = ciexyz_to_ciexyy(*rc)
return rc
def ciexyy_to_srgb(x, y, Y):
'''
Convert CIE xyY to [0, 1] sRGB
@param x:float The x parameter
@param y:float The y parameter
@param Y:float The Y parameter
@return :[float, float, float] The red, green and blue components
'''
rc = ciexyy_to_ciexyz(x, y, Y)
rc = ciexyz_to_linear(*rc)
rc = linear_to_standard(*rc)
return rc
def ciexyz_to_cielab(x, y, z):
'''
Convert from CIE XYZ to CIE L*a*b*
@param x:float The X parameter
@param y:float The Y parameter
@param z:float The Z parameter
@return :[float, float, float] The L*, a* and b* components
'''
x /= 0.95047
z /= 1.08883
f = lambda c : c ** 1 / 3 if c > 0.00885642 else (7.78 + 703 / 99900) * c + 0.1379310
l = 116 * f(Y) - 16
a = 500 * (f(X) - f(Y))
b = 200 * (f(Y) - f(Z))
return (l, a, b)
def cielab_to_xiexyz(l, a, b):
'''
Convert from CIE L*a*b* to CIE XYZ
@param l:float The L* parameter
@param a:float The a* parameter
@param b:float The b* parameter
@return :[float, float, float] The X, Y and Z components
'''
y = (l + 16) / 116
x = a / 500 + y
z = y - b / 200
f = lambda c : c ** 3 if c ** 3 > 0.00885642 else (c - 0.1379310) / (7.78 + 703 / 99900)
(x, y, z) = [f(c) for c in (x, y, z)]
x *= 0.95047
y *= 1.08883
return (x, y, z)
def delta_e(a, b):
'''
Convert the distance (∆E*_ab) between two [0, 1] sRGB colours
@param a:(float, float, float) The first colour
@param b:(float, float, float) The second colour
@return :float The difference
'''
a = standard_to_linear(*a)
b = standard_to_linear(*b)
a = linear_to_ciexyz(*a)
b = linear_to_ciexyz(*b)
a = ciexyz_to_cielab(*a)
b = ciexyz_to_cielab(*b)
return sum([(c1 - c2) ** 2 for c1, c2 in zip(a, b)]) ** 0.5
|
