Source code for colour.models.cie_xyy

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
CIE xyY Colourspace
===================

Defines the *CIE xyY* colourspace transformations:

-   :func:`XYZ_to_xyY`
-   :func:`xyY_to_XYZ`
-   :func:`xy_to_XYZ`
-   :func:`XYZ_to_xy`

See Also
--------
`CIE xyY Colourspace IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/models/cie_xyy.ipynb>`_  # noqa

References
----------
.. [1]  Wikipedia. (n.d.). CIE 1931 color space. Retrieved February 24, 2014,
        from http://en.wikipedia.org/wiki/CIE_1931_color_space
"""

from __future__ import division, unicode_literals

import numpy as np

from colour.colorimetry import ILLUMINANTS
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_xyY',
           'xyY_to_XYZ',
           'xy_to_XYZ',
           'XYZ_to_xy']


[docs]def XYZ_to_xyY(XYZ, illuminant=ILLUMINANTS.get( 'CIE 1931 2 Degree Standard Observer').get('D50')): """ Converts from *CIE XYZ* tristimulus values to *CIE xyY* colourspace and reference *illuminant*. Parameters ---------- XYZ : array_like *CIE XYZ* tristimulus values. illuminant : array_like, optional Reference *illuminant* chromaticity coordinates. Returns ------- ndarray *CIE xyY* colourspace array. Notes ----- - Input *CIE XYZ* tristimulus values are in domain [0, 1]. - Output *CIE xyY* colourspace array is in domain [0, 1]. References ---------- .. [2] Lindbloom, B. (2003). XYZ to xyY. Retrieved February 24, 2014, from http://www.brucelindbloom.com/Eqn_XYZ_to_xyY.html Examples -------- >>> XYZ = np.array([0.07049534, 0.10080000, 0.09558313]) >>> XYZ_to_xyY(XYZ) # doctest: +ELLIPSIS array([ 0.2641477..., 0.3777000..., 0.1008 ]) """ XYZ = np.asarray(XYZ) X, Y, Z = tsplit(XYZ) xy_w = np.asarray(illuminant) XYZ_n = np.zeros(XYZ.shape) XYZ_n[..., 0:2] = xy_w xyY = np.where( np.all(XYZ == 0, axis=-1)[..., np.newaxis], XYZ_n, tstack((X / (X + Y + Z), Y / (X + Y + Z), Y))) return xyY
[docs]def xyY_to_XYZ(xyY): """ Converts from *CIE xyY* colourspace to *CIE XYZ* tristimulus values. Parameters ---------- xyY : array_like *CIE xyY* colourspace array. Returns ------- ndarray *CIE XYZ* tristimulus values. Notes ----- - Input *CIE xyY* colourspace array is in domain [0, 1]. - Output *CIE XYZ* tristimulus values are in domain [0, 1]. References ---------- .. [3] Lindbloom, B. (2009). xyY to XYZ. Retrieved February 24, 2014, from http://www.brucelindbloom.com/Eqn_xyY_to_XYZ.html Examples -------- >>> xyY = np.array([0.26414772, 0.37770001, 0.10080000]) >>> xyY_to_XYZ(xyY) # doctest: +ELLIPSIS array([ 0.0704953..., 0.1008 , 0.0955831...]) """ x, y, Y = tsplit(xyY) XYZ = np.where((y == 0)[..., np.newaxis], tstack((y, y, y)), tstack((x * Y / y, Y, (1 - x - y) * Y / y))) return XYZ
[docs]def xy_to_XYZ(xy): """ Returns the *CIE XYZ* tristimulus values from given *xy* chromaticity coordinates. Parameters ---------- xy : array_like *xy* chromaticity coordinates. Returns ------- ndarray *CIE XYZ* tristimulus values. Notes ----- - Input *xy* chromaticity coordinates are in domain [0, 1]. - Output *CIE XYZ* tristimulus values are in domain [0, 1]. Examples -------- >>> xy = np.array([0.26414772236966133, 0.37770000704815188]) >>> xy_to_XYZ(xy) # doctest: +ELLIPSIS array([ 0.6993585..., 1. , 0.9482453...]) """ x, y = tsplit(xy) xyY = tstack((x, y, np.ones(x.shape))) XYZ = xyY_to_XYZ(xyY) return XYZ
[docs]def XYZ_to_xy(XYZ, illuminant=ILLUMINANTS.get( 'CIE 1931 2 Degree Standard Observer').get('D50')): """ Returns the *xy* chromaticity coordinates from given *CIE XYZ* tristimulus values. Parameters ---------- XYZ : array_like *CIE XYZ* tristimulus values. illuminant : array_like, optional Reference *illuminant* chromaticity coordinates. Returns ------- ndarray *xy* chromaticity coordinates. Notes ----- - Input *CIE XYZ* tristimulus values are in domain [0, 1]. - Output *xy* chromaticity coordinates are in domain [0, 1]. Examples -------- >>> XYZ = np.array([0.07049534, 0.10080000, 0.09558313]) >>> XYZ_to_xy(XYZ) # doctest: +ELLIPSIS array([ 0.2641477..., 0.3777000...]) """ xyY = XYZ_to_xyY(XYZ, illuminant) xy = xyY[..., 0:2] return xy