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]  http://en.wikipedia.org/wiki/CIE_1931_color_space
        (Last accessed 24 February 2014)
"""

from __future__ import division, unicode_literals

import numpy as np

from colour.colorimetry import ILLUMINANTS

__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__ = '[email protected]'
__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* colourspace to *CIE xyY* colourspace and reference *illuminant*. Parameters ---------- XYZ : array_like, (3,) *CIE XYZ* colourspace matrix. illuminant : array_like, optional Reference *illuminant* chromaticity coordinates. Returns ------- ndarray, (3,) *CIE xyY* colourspace matrix. Notes ----- - Input *CIE XYZ* colourspace matrix is in domain [0, 1]. - Output *CIE xyY* colourspace matrix is in domain [0, 1]. References ---------- .. [2] http://www.brucelindbloom.com/Eqn_XYZ_to_xyY.html (Last accessed 24 February 2014) Examples -------- >>> XYZ_to_xyY(np.array([0.1180583421, 0.1034, 0.0515089229])) array([ 0.4325, 0.3788, 0.1034]) """ X, Y, Z = np.ravel(XYZ) if X == 0 and Y == 0 and Z == 0: return np.array([illuminant[0], illuminant[1], Y]) else: return np.array([X / (X + Y + Z), Y / (X + Y + Z), Y])
[docs]def xyY_to_XYZ(xyY): """ Converts from *CIE xyY* colourspace to *CIE XYZ* colourspace. Parameters ---------- xyY : array_like, (3,) *CIE xyY* colourspace matrix. Returns ------- ndarray, (3,) *CIE XYZ* colourspace matrix. Notes ----- - Input *CIE xyY* colourspace matrix is in domain [0, 1]. - Output *CIE XYZ* colourspace matrix is in domain [0, 1]. References ---------- .. [3] http://www.brucelindbloom.com/Eqn_xyY_to_XYZ.html (Last accessed 24 February 2014) Examples -------- >>> xyY_to_XYZ(np.array([0.4325, 0.3788, 0.1034])) # doctest: +ELLIPSIS array([ 0.1180583..., 0.1034 , 0.0515089...]) """ x, y, Y = np.ravel(xyY) if y == 0: return np.array([0, 0, 0]) else: return np.array([x * Y / y, Y, (1 - x - y) * Y / y])
[docs]def xy_to_XYZ(xy): """ Returns the *CIE XYZ* colourspace matrix from given *xy* chromaticity coordinates. Parameters ---------- xy : array_like *xy* chromaticity coordinates. Returns ------- ndarray, (3,) *CIE XYZ* colourspace matrix. Notes ----- - Input *xy* chromaticity coordinates are in domain [0, 1]. - Output *CIE XYZ* colourspace matrix is in domain [0, 1]. Examples -------- >>> xy_to_XYZ((0.25, 0.25)) array([ 1., 1., 2.]) """ return xyY_to_XYZ(np.array([xy[0], xy[1], 1]))
[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* colourspace matrix. Parameters ---------- XYZ : array_like, (3,) *CIE XYZ* colourspace matrix. illuminant : array_like, optional Reference *illuminant* chromaticity coordinates. Returns ------- tuple *xy* chromaticity coordinates. Notes ----- - Input *CIE XYZ* colourspace matrix is in domain [0, 1]. - Output *xy* chromaticity coordinates are in domain [0, 1]. Examples -------- >>> XYZ_to_xy(np.array([0.97137399, 1, 1.04462134])) # doctest: +ELLIPSIS (0.3220741..., 0.3315655...) >>> XYZ_to_xy((0.97137399, 1, 1.04462134)) # doctest: +ELLIPSIS (0.3220741..., 0.3315655...) """ xyY = np.ravel(XYZ_to_xyY(XYZ, illuminant)) return xyY[0], xyY[1]