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#!/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 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
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