#!/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 linear [0, 1] 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 * x / y, Y, 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 ''' p = -Y / X q = 1 + Y / X y = 1 / (p / 2 + (p ** 2 / 4 - q) ** 0.5) x = X * y / Y 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 = 3.2406 * X - 1.5372 * Y - 0.4986 * Z g = -0.9689 * X + 1.8758 * Y + 0.0415 * Z b = 0.0557 * X - 0.2040 * Y + 1.0570 * 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 = 0.4124 * r + 0.3576 * g + 0.1805 * b Y = 0.2126 * r + 0.7152 * g + 0.0722 * b Z = 0.0193 * r + 0.1192 * g + 1.9502 * 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 ''' (r, g, b) = standard_to_linear(r, g, b) (X, Y, Z) = linear_to_ciexyz(r, g, b) return ciexyz_to_ciexyy(X, Y, Z) 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 ''' (X, Y, Z) = ciexyy_to_ciexyz(x, y, Y) (r, g, b) = ciexyz_to_linear(X, Y, Z) return linear_to_standard(r, g, b)