#!/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]