#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
CIE UCS Colourspace
===================
Defines the *CIE UCS* colourspace transformations:
- :func:`XYZ_to_UCS`
- :func:`UCS_to_XYZ`
- :func:`UCS_to_uv`
- :func:`UCS_uv_to_xy`
See Also
--------
`CIE UCS Colourspace IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/models/cie_ucs.ipynb>`_ # noqa
References
----------
.. [1] Wikipedia. (n.d.). CIE 1960 color space. Retrieved February 24, 2014,
from http://en.wikipedia.org/wiki/CIE_1960_color_space
.. [2] Wikipedia. (n.d.). Relation to CIE XYZ. Retrieved February 24, 2014,
from
http://en.wikipedia.org/wiki/CIE_1960_color_space#Relation_to_CIE_XYZ
"""
from __future__ import division, unicode_literals
import numpy as np
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013 - 2014 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = ['XYZ_to_UCS',
'UCS_to_XYZ',
'UCS_to_uv',
'UCS_uv_to_xy']
[docs]def XYZ_to_UCS(XYZ):
"""
Converts from *CIE XYZ* colourspace to *CIE UCS* colourspace.
Parameters
----------
XYZ : array_like, (3,)
*CIE XYZ* colourspace matrix.
Returns
-------
ndarray, (3,)
*CIE UCS* colourspace matrix.
Notes
-----
- Input *CIE XYZ* colourspace matrix is in domain [0, 1].
- Output *CIE UCS* colourspace matrix is in domain [0, 1].
Examples
--------
>>> XYZ = np.array([0.07049534, 0.1008, 0.09558313])
>>> XYZ_to_UCS(XYZ) # doctest: +ELLIPSIS
array([ 0.0469968..., 0.1008 , 0.1637439...])
"""
X, Y, Z = np.ravel(XYZ)
return np.array([2 / 3 * X,
Y,
1 / 2 * (-X + 3 * Y + Z)])
[docs]def UCS_to_XYZ(UVW):
"""
Converts from *CIE UCS* colourspace to *CIE XYZ* colourspace.
Parameters
----------
UVW : array_like, (3,)
*CIE UCS* colourspace matrix.
Returns
-------
ndarray, (3,)
*CIE XYZ* colourspace matrix.
Notes
-----
- Input *CIE UCS* colourspace matrix is in domain [0, 1].
- Output *CIE XYZ* colourspace matrix is in domain [0, 1].
Examples
--------
>>> UVW = np.array([0.04699689, 0.1008, 0.1637439])
>>> UCS_to_XYZ(UVW) # doctest: +ELLIPSIS
array([ 0.0704953..., 0.1008 , 0.0955831...])
"""
U, V, W = np.ravel(UVW)
return np.array(
[3 / 2 * U, V, 3 / 2 * U - (3 * V) + (2 * W)])
[docs]def UCS_to_uv(UVW):
"""
Returns the *uv* chromaticity coordinates from given *CIE UCS* colourspace
matrix.
Parameters
----------
UVW : array_like, (3,)
*CIE UCS* colourspace matrix.
Returns
-------
tuple
*uv* chromaticity coordinates.
Notes
-----
- Input *CIE UCS* colourspace matrix is in domain [0, 1].
- Output *uv* chromaticity coordinates are in domain [0, 1].
Examples
--------
>>> UCS = np.array([0.04699689, 0.1008, 0.1637439])
>>> UCS_to_uv(UCS) # doctest: +ELLIPSIS
(0.1508530..., 0.3235531...)
"""
U, V, W = np.ravel(UVW)
return U / (U + V + W), V / (U + V + W)
[docs]def UCS_uv_to_xy(uv):
"""
Returns the *xy* chromaticity coordinates from given *CIE UCS* colourspace
*uv* chromaticity coordinates.
Parameters
----------
uv : array_like
*CIE UCS uv* chromaticity coordinates.
Returns
-------
tuple
*xy* chromaticity coordinates.
Notes
-----
- Input *uv* chromaticity coordinates are in domain [0, 1].
- Output *xy* chromaticity coordinates are in domain [0, 1].
Examples
--------
>>> uv = (0.15085308732766581, 0.3235531372954405)
>>> UCS_uv_to_xy(uv) # doctest: +ELLIPSIS
(0.2641477..., 0.3777000...)
"""
return (3 * uv[0] / (2 * uv[0] - 8 * uv[1] + 4),
2 * uv[1] / (2 * uv[0] - 8 * uv[1] + 4))
Colour 0.3