#!/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 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 ''' r = 3.24156 * X - 1.53767 * Y - 0.49870 * Z g = -0.96920 * X + 1.87589 * Y + 0.04155 * Z b = 0.05562 * X - 0.20396 * Y + 1.05686 * Z return [r, g, b] 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 ''' X = 0.4123160 * r + 0.3576020 * g + 0.1805010 * b Y = 0.2126000 * r + 0.7151990 * g + 0.0722016 * b Z = 0.0193297 * r + 0.1192040 * g + 0.9506340 * b return [X, Y, Z] 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