Source code for colour.models.cie_ucs

# -*- coding: utf-8 -*-
"""
CIE 1960 UCS Colourspace
========================

Defines the *CIE 1960 UCS* colourspace transformations:

-   :func:`colour.XYZ_to_UCS`
-   :func:`colour.UCS_to_XYZ`
-   :func:`colour.UCS_to_uv`
-   :func:`colour.uv_to_UCS`
-   :func:`colour.UCS_uv_to_xy`
-   :func:`colour.xy_to_UCS_uv`

References
----------
-   :cite:`Wikipedia2008` : Wikipedia. (2008). CIE 1960 color space. Retrieved
    February 24, 2014, from http://en.wikipedia.org/wiki/CIE_1960_color_space
-   :cite:`Wikipedia2008c` : Wikipedia. (2008). Relation to CIE XYZ. Retrieved
    February 24, 2014, from
    http://en.wikipedia.org/wiki/CIE_1960_color_space#Relation_to_CIE_XYZ
"""

from colour.utilities import from_range_1, full, to_domain_1, tsplit, tstack

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2021 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-developers@colour-science.org'
__status__ = 'Production'

__all__ = [
    'XYZ_to_UCS', 'UCS_to_XYZ', 'UCS_to_uv', 'uv_to_UCS', 'UCS_uv_to_xy',
    'xy_to_UCS_uv'
]


[docs]def XYZ_to_UCS(XYZ): """ Converts from *CIE XYZ* tristimulus values to *CIE 1960 UCS* colourspace. Parameters ---------- XYZ : array_like *CIE XYZ* tristimulus values. Returns ------- ndarray *CIE 1960 UCS* colourspace array. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``XYZ`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``UVW`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Wikipedia2008c`, :cite:`Wikipedia2008` Examples -------- >>> import numpy as np >>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952]) >>> XYZ_to_UCS(XYZ) # doctest: +ELLIPSIS array([ 0.1376933..., 0.1219722..., 0.1053731...]) """ X, Y, Z = tsplit(to_domain_1(XYZ)) UVW = tstack([2 / 3 * X, Y, 1 / 2 * (-X + 3 * Y + Z)]) return from_range_1(UVW)
[docs]def UCS_to_XYZ(UVW): """ Converts from *CIE 1960 UCS* colourspace to *CIE XYZ* tristimulus values. Parameters ---------- UVW : array_like *CIE 1960 UCS* colourspace array. Returns ------- ndarray *CIE XYZ* tristimulus values. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``UVW`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``XYZ`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Wikipedia2008c`, :cite:`Wikipedia2008` Examples -------- >>> import numpy as np >>> UVW = np.array([0.13769339, 0.12197225, 0.10537310]) >>> UCS_to_XYZ(UVW) # doctest: +ELLIPSIS array([ 0.2065400..., 0.1219722..., 0.0513695...]) """ U, V, W = tsplit(to_domain_1(UVW)) XYZ = tstack([3 / 2 * U, V, 3 / 2 * U - (3 * V) + (2 * W)]) return from_range_1(XYZ)
[docs]def UCS_to_uv(UVW): """ Returns the *uv* chromaticity coordinates from given *CIE 1960 UCS* colourspace array. Parameters ---------- UVW : array_like *CIE 1960 UCS* colourspace array. Returns ------- ndarray *uv* chromaticity coordinates. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``UVW`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Wikipedia2008c` Examples -------- >>> import numpy as np >>> UVW = np.array([0.13769339, 0.12197225, 0.10537310]) >>> UCS_to_uv(UVW) # doctest: +ELLIPSIS array([ 0.3772021..., 0.3341350...]) """ U, V, W = tsplit(to_domain_1(UVW)) U_V_W = U + V + W uv = tstack([U / U_V_W, V / U_V_W]) return uv
[docs]def uv_to_UCS(uv, V=1): """ Returns the *CIE 1960 UCS* colourspace array from given *uv* chromaticity coordinates. Parameters ---------- uv : array_like *uv* chromaticity coordinates. V : numeric, optional Optional :math:`V` *luminance* value used to construct the *CIE 1960 UCS* colourspace array, the default :math:`V` *luminance* is set to 1. Returns ------- ndarray *CIE 1960 UCS* colourspace array. References ---------- :cite:`Wikipedia2008c` Examples -------- >>> import numpy as np >>> uv = np.array([0.37720213, 0.33413508]) >>> uv_to_UCS(uv) # doctest: +ELLIPSIS array([ 1.1288911..., 1. , 0.8639104...]) """ u, v = tsplit(uv) V = full(u.shape, V) U = V * u / v W = -V * (u + v - 1) / v UVW = tstack([U, V, W]) return from_range_1(UVW)
[docs]def UCS_uv_to_xy(uv): """ Returns the *CIE xy* chromaticity coordinates from given *CIE 1960 UCS* colourspace *uv* chromaticity coordinates. Parameters ---------- uv : array_like *CIE UCS uv* chromaticity coordinates. Returns ------- ndarray *CIE xy* chromaticity coordinates. References ---------- :cite:`Wikipedia2008c` Examples -------- >>> import numpy as np >>> uv = np.array([0.37720213, 0.33413508]) >>> UCS_uv_to_xy(uv) # doctest: +ELLIPSIS array([ 0.5436955..., 0.3210794...]) """ u, v = tsplit(uv) d = 2 * u - 8 * v + 4 xy = tstack([3 * u / d, 2 * v / d]) return xy
[docs]def xy_to_UCS_uv(xy): """ Returns the *CIE 1960 UCS* colourspace *uv* chromaticity coordinates from given *CIE xy* chromaticity coordinates. Parameters ---------- xy : array_like *CIE xy* chromaticity coordinates. Returns ------- ndarray *CIE UCS uv* chromaticity coordinates. References ---------- :cite:`Wikipedia2008c` Examples -------- >>> import numpy as np >>> xy = np.array([0.54369555, 0.32107941]) >>> xy_to_UCS_uv(xy) # doctest: +ELLIPSIS array([ 0.3772021..., 0.3341350...]) """ x, y = tsplit(xy) d = 12 * y - 2 * x + 3 uv = tstack([4 * x / d, 6 * y / d]) return uv