#!/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 ''' # None (except those from the D series) of these # colour temperatures are exact or guaranteed to # even be approximate values. A few of them are # from Wikipedia, others are from very(!) # questionable sources. K_F_LUX_W32_EMBER = 1200 ''' The colour temperature in the Windows port of f.lux named ‘ember’ ''' # Warning: f.lux is nasty software that is extremely # negative in the freedom dimension. Values are not # verified, they are only acquired from f.lux's # “Frequently asked questions”. K_MATCH_FLAME = 1700 ''' Approximate colour temperature of the flame of a match stick @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_CANDLE_FLAME = 1850 ''' Approximate colour temperature of the flame of a candle @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_CANDLELIGHT = K_CANDLE_FLAME ''' Synonym for `K_CANDLE_FLAME` ''' K_SUNSET = 1850 ''' Approximate colour temperature of the sunset @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_SUNRISE = K_SUNSET ''' Approximate colour temperature of the sunrise @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_F_LUX_W32_CANDLE = 1900 ''' The colour temperature in the Windows port of f.lux named ‘candle’ ''' K_HIGH_PRESSURE_SODIUM = 2100 ''' Approximate colour temperature of high pressure sodium ''' K_F_LUX_MAC_CANDLE = 2300 ''' The colour temperature in the Mac OS X and iOS port of f.lux named ‘candle’ ''' K_F_LUX_W32_WARM_INCANDESCENT = 2300 ''' The colour temperature in the Windows port of f.lux named ‘warm incandescent’ ''' K_STANDARD_INCANDESCENT = 2500 ''' Approximate colour of standard incandescent ''' K_INCANDESCENT = K_STANDARD_INCANDESCENT ''' Synonym for `K_STANDARD_INCANDESCENT` ''' K_F_LUX_MAC_TUNGSTEN = 2700 ''' The colour temperature in the Mac OS X and iOS port of f.lux named ‘tungsten’ ''' K_F_LUX_W32_INCANDESCENT = 2700 ''' The colour temperature in the Windows port of f.lux named ‘incandescent’ ''' K_EXTRA_SOFT = 2700 ''' A very soft colour temperature ''' K_PIANO_PIANO_LUX = K_EXTRA_SOFT ''' Synonym for `K_EXTRA_SOFT` and `K_PIANO_PIANO` ''' K_PIANO_PIANO = K_PIANO_PIANO_LUX ''' Synonym for `K_EXTRA_SOFT` and `K_PIANO_PIANO_LUX` ''' K_INCANDESCENT_LAMP = (2700 + 3300) / 2 ''' Approximate average colour temperature of incandescent lamps @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_EARLY_SUNRISE = (2800 + 3200) / 2 ''' Approximate average colour temperature the the sunrise at its early stage ''' K_LATE_SUNSET = K_EARLY_SUNRISE ''' Approximate average colour temperature the the sunsun at its late stage ''' K_WARM_WHITE = 3000 ''' Approximate colour temperature of “warm white” ''' K_SOFT_WHITE_COMPACT_FLOURESCENT_LAMP = 3000 ''' Approximate colour temperature of soft/warm white compact flourescent lamps @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_WARM_WHITE_COMPACT_FLOURESCENT_LAMP = K_SOFT_WHITE_COMPACT_FLOURESCENT_LAMP ''' Synonym for `K_SOFT_WHITE_COMPACT_FLOURESCENT_LAMP` ''' K_HALOGEN_LIGHT = 3000 ''' Approximate colour temperature of halogen light ''' K_TUNGSTEN_LIGHT = 3200 ''' Approximate colour temperature of tungsten light (not to be confused with scheelite) ''' K_HOUSEHOLD_LIGHT_BULB = K_TUNGSTEN_LIGHT ''' Approximate colour temperature regular household light bulbs ''' K_LIGHT_BULB = K_HOUSEHOLD_LIGHT_BULB ''' Synonym for `K_HOUSEHOLD_LIGHT_BULB` ''' K_STUDIO_LAMP = K_TUNGSTEN_LIGHT ''' Approximate colour temperature studio lamps @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_PHOTOFLOOD = K_STUDIO_LAMP ''' Approximate colour temperature photoflood @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_STUDIO_CP_LIGHT = 3350 ''' Approximate colour temperature studio ‘CP’ light @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_F_LUX_MAC_HALOGEN = 3400 ''' The colour temperature in the Mac OS X and iOS port of f.lux named ‘halogen’ ''' K_F_LUX_W32_HALOGEN = 3400 ''' The colour temperature in the Windows port of f.lux named ‘halogen’ ''' K_SOFT = 3700 ''' A soft colour temperature ''' K_PIANO_LUX = K_SOFT ''' Synonym for `K_SOFT` and `K_PIANO` ''' K_PIANO = K_PIANO_LUX ''' Synonym for `K_SOFT` and `K_PIANO_LUX` ''' K_MOONLIGHT = (4100 + 4150) / 2 ''' Approximate average colour temperature of moonlight @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_COOL_WHITE = 4200 ''' Approximate colour temperature of “cool white” ''' K_F_LUX_MAC_FLOURESCENT = 4200 ''' The colour temperature in the Mac OS X and iOS port of f.lux named ‘flourescent’ ''' K_F_LUX_W32_FLOURESCENT = 4200 ''' The colour temperature in the Windows port of f.lux named ‘flourescent’ ''' K_ELECTRONIC_FLASH_BULB = 4500 ''' Approximate colour temperature of electronic flash bulbs ''' K_FLASH_BULB = K_ELECTRONIC_FLASH_BULB ''' Synonym for `K_ELECTRONIC_FLASH_BULB` ''' K_D50 = 5000 ''' The standard illuminant D50 (5000 K) of the CIE standard illuminant series D ''' K_NOON_DAYLIGHT = 5000 ''' Approximate colour temperature of noon daylight ''' K_DIRECT_SUN = K_NOON_DAYLIGHT ''' Approximate colour temperature of direct sunlight ''' K_METAL_HALIDE = 5000 ''' Approximate colour temperature of metal halide ''' K_HORIZON_DAYLIGHT = 5000 ''' Approximate colour temperature of horizon daylight @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_TUBULAR_FLUORESCENT_LAMP = 5000 ''' Approximate colour temperature of tubular fluorescent lamps @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_COOL_WHITE_COMPACT_FLUORESCENT_LAMPS = 5000 ''' Approximate colour temperature of cool white/daylight compact fluorescent lamps @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_DAYLIGHT_WHITE_COMPACT_FLUORESCENT_LAMPS = K_COOL_WHITE_COMPACT_FLUORESCENT_LAMPS ''' Synonym for `K_COOL_WHITE_COMPACT_FLUORESCENT_LAMPS` ''' K_F_LUX_MAC_DAYLIGHT = 5000 ''' The colour temperature in the Mac OS X and iOS port of f.lux named ‘daylight’ ''' K_D55 = 5500 ''' The standard illuminant D55 (5500 K) of the CIE standard illuminant series D ''' K_F_LUX_W32_DAYLIGHT = 5500 ''' The colour temperature in the Windows port of f.lux named ‘daylight’ ''' K_MODERATELY_SOFT = 5500 ''' A moderately soft colour temperature ''' K_MEZZO_PIANO_LUX = K_MODERATELY_SOFT ''' Synonym for `K_MODERATELY_SOFT` and `K_MEZZO_PIANO` ''' K_MEZZO_PIANO = K_MEZZO_PIANO_LUX ''' Synonym for `K_MODERATELY_SOFT` and `K_MEZZO_PIANO_LUX` ''' K_CRYSTAL_VERTICAL = 5600 ''' The colour temperature of the standard lighting of "Kristall, vertikal accent i glas och stål" (Crystal, vertical accent in glass and steal) @ref http://ljusdesign.com/meriter/juryn.htm ''' K_CLEAR_MID_DAY = 5600 ''' Approximate colour temperature of a clear mid-day ''' K_VERTICAL_DAYLIGHT = (5500 + 6000) / 2 ''' Approximate average colour temperature of vertical daylight @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_ELECTRONIC_FLASH = (5500 + 6000) / 2 ''' Approximate average colour temperature of electronic flash @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_XENON_SHORT_ARC_LAMP = 6200 ''' Approximate colour temperature of xenon short-arc lamp @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_DAYLIGHT = 6500 ''' Approximate colour temperature of daylight @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_OVERCAST_DAY = 6500 ''' Approximate colour temperature of daylight during an overcast day @ref https://en.wikipedia.org/wiki/Colour_temperature ''' K_D65 = 6500 ''' The standard illuminant D65 (6500 K) of the CIE standard illuminant series D ''' K_NEUTRAL = K_D65 ''' Synonym for `K_D65`, the standard colour temperature ''' K_WHITE = K_NEUTRAL ''' Synonym for `K_NEUTRAL` ''' K_MEZZO_LUX = K_NEUTRAL ''' A moderate colour temperature ''' K_MEZZO = K_MEZZO_LUX ''' Synonym for `K_MEZZO_LUX` ''' K_SHARP = 7000 ''' A sharp colour temperature ''' K_FORTE_LUX = K_SHARP ''' Synonym for `K_SHARP` and `K_FORTE` ''' K_FORTE = K_FORTE_LUX ''' Synonym for `K_SHARP` and `K_FORTE_LUX` ''' K_D75 = 7500 ''' The standard illuminant D75 (7500 K) of the CIE standard illuminant series D ''' K_BLUE_FILTER = 8000 ''' Approximate colour temperature of a standard blue filter ''' K_NORTH_LIGHT = 10000 ''' Approximate colour temperature of north light ''' K_BLUE_SKY = K_NORTH_LIGHT ''' Synonym for `K_NORTH_LIGHT` ''' K_EXTRA_SHARP = 10000 ''' A very sharp colour temperature ''' K_FORTE_FORTE_LUX = K_EXTRA_SHARP ''' Synonym for `K_EXTRA_SHARP` and `K_FORTE_FORTE` ''' K_FORTE_FORTE = K_FORTE_FORTE_LUX ''' Synonym for `K_EXTRA_SHARP` and `K_FORTE_FORTE_LUX` ''' K_SKYLIGHT = (9000 + 15000) / 2 ''' Approximate average colour temperature of the skylight ''' K_OUTDOOR_SHADE = K_SKYLIGHT ''' Approximate average colour temperature of an outdoor shade ''' K_CLEAR_BLUE_POLEWARD_SKY = (15000 + 27000) / 2 ''' Approximate average colour temperature of a clear blue poleward sky @ref https://en.wikipedia.org/wiki/Colour_temperature ''' 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] def kelvins(temperature): ''' Resolve and colour temperature name @param temperature:float|str The colour temperature @return :float The colour temperature ''' # If float (or something we do not allow) return the input if not isinstance(temperature, str): return temperature # Replace punctuation with underscore temperature = temperature.replace('.', '_').replace('-', '_').replace(' ', '_') # Add prefix and turn into upper case temperature = 'K_' + temperature.upper() # Evaluate (that is, return the named variable) return eval(temperature)