#!/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 .
# This module implements support for colour temperature based
# calculation of white points
import os
import math
from colour import *
# /usr/share/blueshift
DATADIR = 'res'
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
celiing = 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, ceilng)]
# 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> 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]