# -*- coding: utf-8 -*-
"""
Whiteness Index :math:`W`
=========================
Defines *whiteness* index :math:`W` computation objects:
- :func:`colour.colorimetry.whiteness_Berger1959`: *Whiteness* index
:math:`WI` computation of given sample *CIE XYZ* tristimulus values using
*Berger (1959)* method.
- :func:`colour.colorimetry.whiteness_Taube1960`: *Whiteness* index
:math:`WI` computation of given sample *CIE XYZ* tristimulus values using
*Taube (1960)* method.
- :func:`colour.colorimetry.whiteness_Stensby1968`: *Whiteness* index
:math:`WI` computation of given sample *CIE L\\*a\\*b\\** colourspace array
using *Stensby (1968)* method.
- :func:`colour.colorimetry.whiteness_ASTME313`: *Whiteness* index :math:`WI`
of given sample *CIE XYZ* tristimulus values using *ASTM E313* method.
- :func:`colour.colorimetry.whiteness_Ganz1979`: *Whiteness* index :math:`W`
and *tint* :math:`T` computation of given sample *CIE xy* chromaticity
coordinates using *Ganz and Griesser (1979)* method.
- :func:`colour.colorimetry.whiteness_CIE2004`: *Whiteness* :math:`W` or
:math:`W_{10}` and *tint* :math:`T` or :math:`T_{10}` computation of given
sample *CIE xy* chromaticity coordinates using *CIE 2004* method.
- :attr:`colour.WHITENESS_METHODS`: Supported *whiteness* computations
methods.
- :func:`colour.whiteness`: *Whiteness* :math:`W` computation using given
method.
See Also
--------
`Whiteness Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/colorimetry/whiteness.ipynb>`_
References
----------
- :cite:`CIETC1-482004k` : CIE TC 1-48. (2004). The evaluation of whiteness.
In CIE 015:2004 Colorimetry, 3rd Edition (p. 24). ISBN:978-3-901-90633-6
- :cite:`Wyszecki2000ba` : Wyszecki, G., & Stiles, W. S. (2000).
Table I(6.5.3) Whiteness Formulae (Whiteness Measure Denoted by W). In
Color Science: Concepts and Methods, Quantitative Data and Formulae
(pp. 837-839). Wiley. ISBN:978-0471399186
- :cite:`X-Rite2012a` : X-Rite, & Pantone. (2012). Color iQC and Color
iMatch Color Calculations Guide. Retrieved from
https://www.xrite.com/-/media/xrite/files/\
apps_engineering_techdocuments/c/09_color_calculations_en.pdf
- :cite:`Wikipedia2004b` : Wikipedia. (2004). Whiteness. Retrieved September
17, 2014, from http://en.wikipedia.org/wiki/Whiteness
"""
from __future__ import division, unicode_literals
from colour.utilities import (CaseInsensitiveMapping, get_domain_range_scale,
filter_kwargs, from_range_100, to_domain_100,
tsplit, tstack)
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - 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__ = [
'whiteness_Berger1959', 'whiteness_Taube1960', 'whiteness_Stensby1968',
'whiteness_ASTME313', 'whiteness_Ganz1979', 'whiteness_CIE2004',
'WHITENESS_METHODS', 'whiteness'
]
[docs]def whiteness_Berger1959(XYZ, XYZ_0):
"""
Returns the *whiteness* index :math:`WI` of given sample *CIE XYZ*
tristimulus values using *Berger (1959)* method.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values of sample.
XYZ_0 : array_like
*CIE XYZ* tristimulus values of reference white.
Returns
-------
numeric or ndarray
*Whiteness* :math:`WI`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``XYZ`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
| ``XYZ_0`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``WI`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
- *Whiteness* :math:`WI` values larger than 33.33 indicate a bluish
white and values smaller than 33.33 indicate a yellowish white.
References
----------
:cite:`X-Rite2012a`
Examples
--------
>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> XYZ_0 = np.array([94.80966767, 100.00000000, 107.30513595])
>>> whiteness_Berger1959(XYZ, XYZ_0) # doctest: +ELLIPSIS
30.3638017...
"""
X, Y, Z = tsplit(to_domain_100(XYZ))
X_0, _Y_0, Z_0 = tsplit(to_domain_100(XYZ_0))
WI = 0.333 * Y + 125 * (Z / Z_0) - 125 * (X / X_0)
return from_range_100(WI)
[docs]def whiteness_Taube1960(XYZ, XYZ_0):
"""
Returns the *whiteness* index :math:`WI` of given sample *CIE XYZ*
tristimulus values using *Taube (1960)* method.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values of sample.
XYZ_0 : array_like
*CIE XYZ* tristimulus values of reference white.
Returns
-------
numeric or ndarray
*Whiteness* :math:`WI`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``XYZ`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
| ``XYZ_0`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``WI`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
- *Whiteness* :math:`WI` values larger than 100 indicate a bluish
white and values smaller than 100 indicate a yellowish white.
References
----------
:cite:`X-Rite2012a`
Examples
--------
>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> XYZ_0 = np.array([94.80966767, 100.00000000, 107.30513595])
>>> whiteness_Taube1960(XYZ, XYZ_0) # doctest: +ELLIPSIS
91.4071738...
"""
_X, Y, Z = tsplit(to_domain_100(XYZ))
_X_0, _Y_0, Z_0 = tsplit(to_domain_100(XYZ_0))
WI = 400 * (Z / Z_0) - 3 * Y
return from_range_100(WI)
[docs]def whiteness_Stensby1968(Lab):
"""
Returns the *whiteness* index :math:`WI` of given sample *CIE L\\*a\\*b\\**
colourspace array using *Stensby (1968)* method.
Parameters
----------
Lab : array_like
*CIE L\\*a\\*b\\** colourspace array of sample.
Returns
-------
numeric or ndarray
*Whiteness* :math:`WI`.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] |
| | | |
| | ``a`` : [-100, 100] | ``a`` : [-1, 1] |
| | | |
| | ``b`` : [-100, 100] | ``b`` : [-1, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``WI`` | [0, 100] | [0, 1] |
+------------+-----------------------+-----------------+
- *Whiteness* :math:`WI` values larger than 100 indicate a bluish
white and values smaller than 100 indicate a yellowish white.
References
----------
:cite:`X-Rite2012a`
Examples
--------
>>> import numpy as np
>>> Lab = np.array([100.00000000, -2.46875131, -16.72486654])
>>> whiteness_Stensby1968(Lab) # doctest: +ELLIPSIS
142.7683456...
"""
L, a, b = tsplit(to_domain_100(Lab))
WI = L - 3 * b + 3 * a
return from_range_100(WI)
[docs]def whiteness_ASTME313(XYZ):
"""
Returns the *whiteness* index :math:`WI` of given sample *CIE XYZ*
tristimulus values using *ASTM E313* method.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values of sample.
Returns
-------
numeric or ndarray
*Whiteness* :math:`WI`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``XYZ`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``WI`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`X-Rite2012a`
Examples
--------
>>> import numpy as np
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> whiteness_ASTME313(XYZ) # doctest: +ELLIPSIS
55.7400000...
"""
_X, Y, Z = tsplit(to_domain_100(XYZ))
WI = 3.388 * Z - 3 * Y
return from_range_100(WI)
[docs]def whiteness_Ganz1979(xy, Y):
"""
Returns the *whiteness* index :math:`W` and *tint* :math:`T` of given
sample *CIE xy* chromaticity coordinates using *Ganz and Griesser (1979)*
method.
Parameters
----------
xy : array_like
Chromaticity coordinates *CIE xy* of sample.
Y : numeric or array_like
Tristimulus :math:`Y` value of sample.
Returns
-------
ndarray
*Whiteness* :math:`W` and *tint* :math:`T`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``Y`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``WT`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
- The formula coefficients are valid for
*CIE Standard Illuminant D Series* *D65* and
*CIE 1964 10 Degree Standard Observer*.
- Positive output *tint* :math:`T` values indicate a greener tint while
negative values indicate a redder tint.
- Whiteness differences of less than 5 Ganz units appear to be
indistinguishable to the human eye.
- Tint differences of less than 0.5 Ganz units appear to be
indistinguishable to the human eye.
References
----------
:cite:`X-Rite2012a`
Examples
--------
>>> import numpy as np
>>> xy = np.array([0.3167, 0.3334])
>>> whiteness_Ganz1979(xy, 100) # doctest: +ELLIPSIS
array([ 85.6003766..., 0.6789003...])
"""
x, y = tsplit(xy)
Y = to_domain_100(Y)
W = Y - 1868.322 * x - 3695.690 * y + 1809.441
T = -1001.223 * x + 748.366 * y + 68.261
WT = tstack([W, T])
return from_range_100(WT)
[docs]def whiteness_CIE2004(xy,
Y,
xy_n,
observer='CIE 1931 2 Degree Standard Observer'):
"""
Returns the *whiteness* :math:`W` or :math:`W_{10}` and *tint* :math:`T`
or :math:`T_{10}` of given sample *CIE xy* chromaticity coordinates using
*CIE 2004* method.
Parameters
----------
xy : array_like
Chromaticity coordinates *CIE xy* of sample.
Y : numeric or array_like
Tristimulus :math:`Y` value of sample.
xy_n : array_like
Chromaticity coordinates *xy_n* of perfect diffuser.
observer : unicode, optional
**{'CIE 1931 2 Degree Standard Observer',
'CIE 1964 10 Degree Standard Observer'}**,
*CIE Standard Observer* used for computations, *tint* :math:`T` or
:math:`T_{10}` value is dependent on viewing field angular subtense.
Returns
-------
ndarray
*Whiteness* :math:`W` or :math:`W_{10}` and *tint* :math:`T` or
:math:`T_{10}` of given sample.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``Y`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``WT`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
- This method may be used only for samples whose values of :math:`W` or
:math:`W_{10}` lie within the following limits: greater than 40 and
less than 5Y - 280, or 5Y10 - 280.
- This method may be used only for samples whose values of :math:`T` or
:math:`T_{10}` lie within the following limits: greater than -4 and
less than +2.
- Output *whiteness* :math:`W` or :math:`W_{10}` values larger than 100
indicate a bluish white while values smaller than 100 indicate a
yellowish white.
- Positive output *tint* :math:`T` or :math:`T_{10}` values indicate a
greener tint while negative values indicate a redder tint.
References
----------
:cite:`CIETC1-482004k`
Examples
--------
>>> import numpy as np
>>> xy = np.array([0.3167, 0.3334])
>>> xy_n = np.array([0.3139, 0.3311])
>>> whiteness_CIE2004(xy, 100, xy_n) # doctest: +ELLIPSIS
array([ 93.85..., -1.305...])
"""
x, y = tsplit(xy)
Y = to_domain_100(Y)
x_n, y_n = tsplit(xy_n)
W = Y + 800 * (x_n - x) + 1700 * (y_n - y)
T = (1000 if '1931' in observer else 900) * (x_n - x) - 650 * (y_n - y)
WT = tstack([W, T])
return from_range_100(WT)
WHITENESS_METHODS = CaseInsensitiveMapping({
'Berger 1959': whiteness_Berger1959,
'Taube 1960': whiteness_Taube1960,
'Stensby 1968': whiteness_Stensby1968,
'ASTM E313': whiteness_ASTME313,
'Ganz 1979': whiteness_Ganz1979,
'CIE 2004': whiteness_CIE2004
})
WHITENESS_METHODS.__doc__ = """
Supported *whiteness* computation methods.
References
----------
:cite:`CIETC1-482004k`, :cite:`X-Rite2012a`
WHITENESS_METHODS : CaseInsensitiveMapping
**{'CIE 2004', 'Berger 1959', 'Taube 1960', 'Stensby 1968', 'ASTM E313',
'Ganz 1979', 'CIE 2004'}**
Aliases:
- 'cie2004': 'CIE 2004'
"""
WHITENESS_METHODS['cie2004'] = WHITENESS_METHODS['CIE 2004']
[docs]def whiteness(XYZ, XYZ_0, method='CIE 2004', **kwargs):
"""
Returns the *whiteness* :math:`W` using given method.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values of sample.
XYZ_0 : array_like
*CIE XYZ* tristimulus values of reference white.
method : unicode, optional
**{'CIE 2004', 'Berger 1959', 'Taube 1960', 'Stensby 1968',
'ASTM E313', 'Ganz 1979'}**,
Computation method.
Other Parameters
----------------
observer : unicode, optional
{:func:`colour.colorimetry.whiteness_CIE2004`},
**{'CIE 1931 2 Degree Standard Observer',
'CIE 1964 10 Degree Standard Observer'}**,
*CIE Standard Observer* used for computations, *tint* :math:`T` or
:math:`T_{10}` value is dependent on viewing field angular subtense.
Returns
-------
numeric or ndarray
*whiteness* :math:`W`.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
+------------+-----------------------+-----------------+
| ``XYZ`` | [0, 100] | [0, 1] |
+------------+-----------------------+-----------------+
| ``XYZ_0`` | [0, 100] | [0, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``W`` | [0, 100] | [0, 1] |
+------------+-----------------------+-----------------+
References
----------
:cite:`CIETC1-482004k`, :cite:`Wyszecki2000ba`, :cite:`X-Rite2012a`,
:cite:`Wikipedia2004b`
Examples
--------
>>> import numpy as np
>>> from colour.models import xyY_to_XYZ
>>> XYZ = xyY_to_XYZ(np.array([0.3167, 0.3334, 100]))
>>> XYZ_0 = xyY_to_XYZ(np.array([0.3139, 0.3311, 100]))
>>> whiteness(XYZ, XYZ_0) # doctest: +ELLIPSIS
array([ 93.85..., -1.305...])
>>> XYZ = np.array([95.00000000, 100.00000000, 105.00000000])
>>> XYZ_0 = np.array([94.80966767, 100.00000000, 107.30513595])
>>> whiteness(XYZ, XYZ_0, method='Taube 1960') # doctest: +ELLIPSIS
91.4071738...
"""
kwargs.update({'XYZ': XYZ, 'XYZ_0': XYZ_0})
function = WHITENESS_METHODS.get(method)
if function is whiteness_Stensby1968:
from colour.models import XYZ_to_Lab, XYZ_to_xy
if get_domain_range_scale() == 'reference':
XYZ = XYZ / 100
XYZ_0 = XYZ_0 / 100
kwargs.update({'Lab': XYZ_to_Lab(XYZ, XYZ_to_xy(XYZ_0))})
elif function in (whiteness_Ganz1979, whiteness_CIE2004):
from colour.models import XYZ_to_xy
_X_0, Y_0, _Z_0 = tsplit(XYZ_0)
kwargs.update({
'xy': XYZ_to_xy(XYZ),
'Y': Y_0,
'xy_n': XYZ_to_xy(XYZ_0)
})
return function(**filter_kwargs(function, **kwargs))