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
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
#!/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/>.
# This module implements support for colour temperature based
# calculation of white points
import os
import math
from colour import *
DATADIR = 'res'
'''
:str The path to program resources, '/usr/share/blueshift' is standard
'''
def series_d(temperature):
'''
Calculate the colour for a blackbody temperature
Using `lambda t : divide_by_maximum(series_d(t))` as the algorithm is better than just `series_d`
@param temperature:float The blackbody temperature in kelvins, must be inside [4000, 7000]
@return :(float, float, float) The red, green and blue components of the white point
'''
# Get coefficients for calculating the x component
# of the colour in the CIE xyY colour space
x, ks = 0, (0.244063, 0.09911, 2.9678, -4.6070)
if temperature > 7000:
ks = (0.237040, 0.24748, 1.9018, -2.0064)
# Calculate the x component of the colour in the CIE xyY colour space
for d, k in enumerate(ks):
x += k * 10 ** (d * 3) / temperature ** d
# Calculate the y component of the colour in the CIE xyY colour space
y = 2.870 * x - 3.000 * x ** 2 - 0.275
# Convert to sRGB and return, with full illumination
return ciexyy_to_srgb(x, y, 1.0)
def simple_whitepoint(temperature):
'''
Calculate the colour for a blackbody temperature using a simple algorithm
@param temperature:float The blackbody temperature in kelvins, not guaranteed for values outside [1000, 40000]
@return :(float, float, float) The red, green and blue components of the white point
'''
r, g, b, temp = 1, 1, 1, temperature / 100
if temp > 66:
r = 1.292936186 * (temp - 60) ** 0.1332047592
g = 1.129890861 * (temp - 60) ** -0.0755148492
else:
g = 0.390081579 * math.log(temp) - 0.631841444
if temp < 66:
b = 0 if temp <= 19 else 0.543206789 * math.log(temp - 10) - 1.196254089
return (r, g, b)
cmf_2deg_cache = None
def cmf_2deg(temperature):
'''
Calculate the colour for a blackbody temperature using raw CIE 1931 2 degree CMF data with interpolation
Using `lambda t : divide_by_maximum(cmf_2deg(t))` as the algorithm is better than just `cmf_2deg`,
`lambda t : clip_whitepoint(divide_by_maximum(cmf_2deg(t)))` is even better if you plan to use really
low temperatures,
@param temperature:float The blackbody temperature in kelvins, clipped to [1000, 40000]
@return :(float, float, float) The red, green and blue components of the white point
'''
global cmf_2deg_cache
if cmf_2deg_cache is None:
# Load, parse and cache lookup table if not cached
cmf_2deg_cache = get_blackbody_lut('2deg')
# Calculate whitepoint
return cmf_xdeg(temperature, cmf_2deg_cache)
cmf_10deg_cache = None
def cmf_10deg(temperature):
'''
Calculate the colour for a blackbody temperature using raw CIE 1964 10 degree CMF data with interpolation
Using `lambda t : divide_by_maximum(cmf_10deg(t))` as the algorithm is better than just `cmf_10deg`,
`lambda t : clip_whitepoint(divide_by_maximum(cmf_10deg(t)))` is even better if you plan to use really
low temperatures,
@param temperature:float The blackbody temperature in kelvins, clipped to [1000, 40000]
@return :(float, float, float) The red, green and blue components of the white point
'''
global cmf_10deg_cache
if cmf_10deg_cache is None:
# Load, parse and cache lookup table if not cached
cmf_10deg_cache = get_blackbody_lut('10deg')
# Calculate whitepoint
return cmf_xdeg(temperature, cmf_10deg_cache)
def cmf_xdeg(temperature, lut, temp_min = 1000, temp_max = 40000, temp_step = 100):
'''
Calculate the colour for a blackbody temperature using
raw data in the CIE xyY colour space with interpolation
This function is intended as help functions for the two functions above this one in this module
@param temperature:float The blackbody temperature in kelvins
@param lut:list<[x:float, y:float]> Raw data lookup table
@param temp_min:float The lowest temperature in the lookup table
@param temp_max:float The highest temperature in the lookup table
@param temp_step:float The interval between the temperatures
@return :(r:float, g:float, b:float) The whitepoint in [0, 1] sRGB
'''
# Clip temperature to definition domain and remove offset
x, y, temp = 0, 0, min(max(temp_min, temperature), temp_max) - temp_min
if temp % temp_step == 0:
# Exact temperature is included in the lookup table
(x, y) = lut[int(temp // temp_step)]
else:
# x component floor and y component floor
floor = lut[int(temp // temp_step)]
# x component ceiling and y component ceiling
ceiling = lut[int(temp // temp_step + 1)]
# Weight
temp = (temp % temp_step) / temp_step
# Interpolation
(x, y) = [c1 * (1 - temp) + c2 * temp for c1, c2 in zip(floor, ceiling)]
# Convert to sRGB
return ciexyy_to_srgb(x, y, 1.0)
redshift_cache, redshift_old_cache = None, None
def redshift(temperature, old_version = False, linear_interpolation = False):
'''
Calculate the colour for a blackbody temperature using same data as in the program redshift
@param temperature:float The blackbody temperature in kelvins, clipped to [1000, 25100] (100 more kelvins than in redshift)
@param old_version:bool Whether to the method used in redshift<=1.8, in which case
`temperature` is clipped to [1000, 10000] (1 more kelvin than in redshift)
@param linear_interpolation:bool Whether to interpolate one linear RGB instead of sRGB
@return :(float, float, float) The red, green and blue components of the white point
'''
global redshift_cache, redshift_old_cache
# Retrieve cache
cache = redshift_old_cache if old_version else redshift_cache
if cache is None:
# Load and parse lookup table if not cached
cache = get_blackbody_lut('redshift_old' if old_version else 'redshift')
# Cache lookup table
if old_version: redshift_old_cache = cache
else: redshift_cache = cache
# Clip to definition domain and remove offset
temp = min(max(1000, temperature), 10000 if old_version else 25100) - 1000
r, g, b = 1, 1, 1
if (temp % 100) == 0:
# Exact temperature is included in the lookup table
(r, g, b) = cache[int(temp // 100)]
else:
# Floor
rgb1 = cache[int(temp // 100)]
# Ceiling
rgb2 = cache[int(temp // 100 + 1)]
# Weight
temp = (temp % 100) / 100
# Interpolation
if linear_interpolation:
(rgb1, rgb2) = [standard_to_linear(*rgb) for rgb in (rgb1, rgb2)]
(r, g, b) = [c1 * (1 - temp) + c2 * temp for c1, c2 in zip(rgb1, rgb2)]
if linear_interpolation:
(r, g, b) = linear_to_standard(r, g, b)
return (r, g, b)
def get_blackbody_lut(filename):
'''
Load and parse a blackbody data lookup table
This function is intended as help functions for the functions above this one in this module
@param filename:str The filename of the lookup table
@return :list<list<float>> A float matrix of all values in the lookup table
'''
# Load lookup table
lut = None
with open(DATADIR + os.sep + filename, 'rb') as file:
lut = file.read().decode('utf-8', 'error').split('\n')
# Parse lookup table
return [[float(cell) for cell in line.split(' ')] for line in lut if not line == '']
def divide_by_maximum(rgb):
'''
Divide all colour components by the value of the most prominent colour component
@param rgb:[float, float, float] The three colour components
@return :[float, float, float] The three colour components divided by the maximum
'''
m = max([abs(x) for x in rgb])
return rgb if m == 0 else [x / m for x in rgb]
def clip_whitepoint(rgb):
'''
Clip all colour components to fit inside [0, 1]
@param rgb:[float, float, float] The three colour components
@return :[float, float, float] The three colour components clipped
'''
return [min(max(0, x), 1) for x in rgb]
|
