#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
CIE UVW Colourspace
===================
Defines the *CIE U\*V\*W\** colourspace transformations:
- :func:`XYZ_to_UVW`
See Also
--------
`CIE UVW Colourspace IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/models/cie_uvw.ipynb>`_ # noqa
References
----------
.. [1] Wikipedia. (n.d.). CIE 1964 color space. Retrieved June 10, 2014, from
http://en.wikipedia.org/wiki/CIE_1964_color_space
"""
from __future__ import division, unicode_literals
from colour.colorimetry import ILLUMINANTS
from colour.models import (
UCS_to_uv,
XYZ_to_UCS,
XYZ_to_xyY,
xy_to_xyY,
xyY_to_XYZ,
xyY_to_xy)
from colour.utilities import tsplit, tstack
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013 - 2015 - 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_UVW']
[docs]def XYZ_to_UVW(XYZ,
illuminant=ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get('D50')):
"""
Converts from *CIE XYZ* tristimulus values to *CIE 1964 U\*V\*W\**
colourspace.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values.
illuminant : array_like, optional
Reference *illuminant* *xy* chromaticity coordinates or *CIE xyY*
colourspace array.
Returns
-------
ndarray
*CIE 1964 U\*V\*W\** colourspace array.
Notes
-----
- Input *CIE XYZ* tristimulus values are in domain [0, 100].
- Input *illuminant* *xy* chromaticity coordinates or *CIE xyY*
colourspace array are in domain [0, :math:`\infty`].
- Output *CIE UVW* colourspace array is in domain [0, 100].
Warning
-------
The input / output domains of that definition are non standard!
Examples
--------
>>> import numpy as np
>>> XYZ = np.array([0.07049534, 0.10080000, 0.09558313]) * 100
>>> XYZ_to_UVW(XYZ) # doctest: +ELLIPSIS
array([-28.0483277..., -0.8805242..., 37.0041149...])
"""
xyY = XYZ_to_xyY(XYZ, xyY_to_xy(illuminant))
_x, y, Y = tsplit(xyY)
u, v = tsplit(UCS_to_uv(XYZ_to_UCS(XYZ)))
u_0, v_0 = tsplit(UCS_to_uv(XYZ_to_UCS(
xyY_to_XYZ(xy_to_xyY(illuminant)))))
W = 25 * Y ** (1 / 3) - 17
U = 13 * W * (u - u_0)
V = 13 * W * (v - v_0)
UVW = tstack((U, V, W))
return UVW
Colour 0.3