Source code for colour.colorimetry.luminance

# -*- coding: utf-8 -*-
"""
Luminance :math:`Y`
===================

Defines *luminance* :math:`Y` computation objects.

The following methods are available:

-   :func:`colour.colorimetry.luminance_Newhall1943`: *luminance* :math:`Y`
    computation of given *Munsell* value :math:`V` using
    *Newhall, Nickerson and Judd (1943)* method.
-   :func:`colour.colorimetry.luminance_ASTMD1535`: *luminance* :math:`Y`
    computation of given *Munsell* value :math:`V` using *ASTM D1535-08e1*
    method.
-   :func:`colour.colorimetry.luminance_CIE1976`: *luminance* :math:`Y`
    computation of given *Lightness* :math:`L^*` as per *CIE 1976*
    recommendation.
-   :func:`colour.colorimetry.luminance_Fairchild2010`: *luminance* :math:`Y`
    computation of given *Lightness* :math:`L_{hdr}` using
    *Fairchild and Wyble (2010)* method.
-   :func:`colour.colorimetry.luminance_Fairchild2011`: *luminance* :math:`Y`
    computation of given *Lightness* :math:`L_{hdr}` using
    *Fairchild and Chen (2011)* method.
-   :attr:`colour.LUMINANCE_METHODS`: Supported *luminance* :math:`Y`
    computation methods.
-   :func:`colour.luminance`: *Luminance* :math:`Y` computation of given
    *Lightness* :math:`L^*` or given *Munsell* value :math:`V` using given
    method.

See Also
--------
`Luminance Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/colorimetry/luminance.ipynb>`_

References
----------
-   :cite:`ASTMInternational2008a` : ASTM International. (2008).
    ASTM D1535-08e1 - Standard Practice for Specifying Color by the Munsell
    System. doi:10.1520/D1535-08E01
-   :cite:`CIETC1-482004m` : CIE TC 1-48. (2004). CIE 1976 uniform colour
    spaces. In CIE 015:2004 Colorimetry, 3rd Edition (p. 24).
    ISBN:978-3-901-90633-6
-   :cite:`Fairchild2010` : Fairchild, M. D., & Wyble, D. R. (2010).
    hdr-CIELAB and hdr-IPT: Simple Models for Describing the Color of
    High-Dynamic-Range and Wide-Color-Gamut Images. In Proc. of Color and
    Imaging Conference (pp. 322-326). ISBN:9781629932156
-   :cite:`Fairchild2011` : Fairchild, M. D., & Chen, P. (2011). Brightness,
    lightness, and specifying color in high-dynamic-range scenes and images.
    In S. P. Farnand & F. Gaykema (Eds.), Proc. SPIE 7867, Image Quality and
    System Performance VIII (p. 78670O). doi:10.1117/12.872075
-   :cite:`Newhall1943a` : Newhall, S. M., Nickerson, D., & Judd, D. B. (1943).
    Final Report of the OSA Subcommittee on the Spacing of the Munsell Colors.
    Journal of the Optical Society of America, 33(7), 385.
    doi:10.1364/JOSA.33.000385
-   :cite:`Wikipedia2001b` : Wikipedia. (2001). Luminance. Retrieved February
    10, 2018, from https://en.wikipedia.org/wiki/Luminance
-   :cite:`Wyszecki2000bd` : Wyszecki, G., & Stiles, W. S. (2000). CIE 1976
    (L*u*v*)-Space and Color-Difference Formula. In Color Science: Concepts and
    Methods, Quantitative Data and Formulae (p. 167). Wiley.
    ISBN:978-0471399186
"""

from __future__ import division, unicode_literals

import numpy as np

from colour.biochemistry import substrate_concentration_MichealisMenten
from colour.utilities import (CaseInsensitiveMapping, as_float_array, as_float,
                              filter_kwargs, from_range_1, from_range_100,
                              get_domain_range_scale, to_domain_10,
                              to_domain_100)

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2019 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = '[email protected]'
__status__ = 'Production'

__all__ = [
    'luminance_Newhall1943', 'luminance_ASTMD1535',
    'intermediate_luminance_function_CIE1976', 'luminance_CIE1976',
    'luminance_Fairchild2010', 'luminance_Fairchild2011', 'LUMINANCE_METHODS',
    'luminance'
]


[docs]def luminance_Newhall1943(V): """ Returns the *luminance* :math:`R_Y` of given *Munsell* value :math:`V` using *Newhall et al. (1943)* method. Parameters ---------- V : numeric or array_like *Munsell* value :math:`V`. Returns ------- numeric or array_like *luminance* :math:`R_Y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 10] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``R_Y`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Newhall1943a` Examples -------- >>> luminance_Newhall1943(4.08244375) # doctest: +ELLIPSIS 12.5500788... """ V = to_domain_10(V) R_Y = (1.2219 * V - 0.23111 * (V * V) + 0.23951 * (V ** 3) - 0.021009 * (V ** 4) + 0.0008404 * (V ** 5)) return from_range_100(R_Y)
[docs]def luminance_ASTMD1535(V): """ Returns the *luminance* :math:`Y` of given *Munsell* value :math:`V` using *ASTM D1535-08e1* method. Parameters ---------- V : numeric or array_like *Munsell* value :math:`V`. Returns ------- numeric or array_like *luminance* :math:`Y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 10] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``Y`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`ASTMInternational2008a` Examples -------- >>> luminance_ASTMD1535(4.08244375) # doctest: +ELLIPSIS 12.2363426... """ V = to_domain_10(V) Y = (1.1914 * V - 0.22533 * (V ** 2) + 0.23352 * (V ** 3) - 0.020484 * (V ** 4) + 0.00081939 * (V ** 5)) return from_range_100(Y)
[docs]def intermediate_luminance_function_CIE1976(f_Y_Y_n, Y_n=100): """ Returns the *luminance* :math:`Y` in the *luminance* :math:`Y` computation for given intermediate value :math:`f(Y/Yn)` using given reference white *luminance* :math:`Y_n` as per *CIE 1976* recommendation. Parameters ---------- f_Y_Y_n : numeric or array_like Intermediate value :math:`f(Y/Yn)`. Y_n : numeric or array_like White reference *luminance* :math:`Y_n`. Returns ------- numeric or array_like *luminance* :math:`Y`. Notes ----- +-------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=============+=======================+===============+ | ``f_Y_Y_n`` | [0, 1] | [0, 1] | +-------------+-----------------------+---------------+ +-------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=============+=======================+===============+ | ``Y`` | [0, 100] | [0, 100] | +-------------+-----------------------+---------------+ References ---------- :cite:`CIETC1-482004m`, :cite:`Wyszecki2000bd` Examples -------- >>> intermediate_luminance_function_CIE1976(0.495929964178047) ... # doctest: +ELLIPSIS 12.1972253... >>> intermediate_luminance_function_CIE1976(0.504482161449319, 95) ... # doctest: +ELLIPSIS 12.1972253... """ f_Y_Y_n = as_float_array(f_Y_Y_n) Y_n = as_float_array(Y_n) Y = as_float( np.where( f_Y_Y_n > 24 / 116, Y_n * f_Y_Y_n ** 3, Y_n * (f_Y_Y_n - 16 / 116) * (108 / 841), )) return Y
[docs]def luminance_CIE1976(L_star, Y_n=100): """ Returns the *luminance* :math:`Y` of given *Lightness* :math:`L^*` with given reference white *luminance* :math:`Y_n`. Parameters ---------- L_star : numeric or array_like *Lightness* :math:`L^*` Y_n : numeric or array_like White reference *luminance* :math:`Y_n`. Returns ------- numeric or array_like *luminance* :math:`Y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_star`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``Y`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`CIETC1-482004m`, :cite:`Wyszecki2000bd` Examples -------- >>> luminance_CIE1976(41.527875844653451) # doctest: +ELLIPSIS 12.1972253... >>> luminance_CIE1976(41.527875844653451, 95) # doctest: +ELLIPSIS 11.5873640... """ L_star = to_domain_100(L_star) Y_n = as_float_array(Y_n) f_Y_Y_n = (L_star + 16) / 116 Y = intermediate_luminance_function_CIE1976(f_Y_Y_n, Y_n) return from_range_100(Y)
[docs]def luminance_Fairchild2010(L_hdr, epsilon=1.836): """ Computes *luminance* :math:`Y` of given *Lightness* :math:`L_{hdr}` using *Fairchild and Wyble (2010)* method according to *Michealis-Menten* kinetics. Parameters ---------- L_hdr : array_like *Lightness* :math:`L_{hdr}`. epsilon : numeric or array_like, optional :math:`\\epsilon` exponent. Returns ------- array_like *luminance* :math:`Y`. Warning ------- The output range of that definition is non standard! Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_hdr`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``Y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Fairchild2010` Examples -------- >>> luminance_Fairchild2010(31.996390226262736, 1.836) ... # doctest: +ELLIPSIS 0.1219722... """ L_hdr = to_domain_100(L_hdr) Y = np.exp( np.log( substrate_concentration_MichealisMenten(L_hdr - 0.02, 100, 0.184 ** epsilon)) / epsilon) return from_range_1(Y)
[docs]def luminance_Fairchild2011(L_hdr, epsilon=0.474, method='hdr-CIELAB'): """ Computes *luminance* :math:`Y` of given *Lightness* :math:`L_{hdr}` using *Fairchild and Chen (2011)* method according to *Michealis-Menten* kinetics. Parameters ---------- L_hdr : array_like *Lightness* :math:`L_{hdr}`. epsilon : numeric or array_like, optional :math:`\\epsilon` exponent. method : unicode, optional **{'hdr-CIELAB', 'hdr-IPT'}**, *Lightness* :math:`L_{hdr}` computation method. Returns ------- array_like *luminance* :math:`Y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_hdr`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``Y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Fairchild2011` Examples -------- >>> luminance_Fairchild2011(51.852958445912506) # doctest: +ELLIPSIS 0.1219722... >>> luminance_Fairchild2011(51.643108411718522, method='hdr-IPT') ... # doctest: +ELLIPSIS 0.1219722... """ L_hdr = to_domain_100(L_hdr) if method.lower() == 'hdr-cielab': maximum_perception = 247 else: maximum_perception = 246 Y = np.exp( np.log( substrate_concentration_MichealisMenten( L_hdr - 0.02, maximum_perception, 2 ** epsilon)) / epsilon) return from_range_1(Y)
LUMINANCE_METHODS = CaseInsensitiveMapping({ 'Newhall 1943': luminance_Newhall1943, 'ASTM D1535': luminance_ASTMD1535, 'CIE 1976': luminance_CIE1976, 'Fairchild 2010': luminance_Fairchild2010, 'Fairchild 2011': luminance_Fairchild2011 }) LUMINANCE_METHODS.__doc__ = """ Supported *luminance* computation methods. References ---------- :cite:`ASTMInternational2008a`, :cite:`CIETC1-482004m`, :cite:`Fairchild2010`, :cite:`Fairchild2011`, :cite:`Newhall1943a`, :cite:`Wyszecki2000bd` LUMINANCE_METHODS : CaseInsensitiveMapping **{'Newhall 1943', 'ASTM D1535', 'CIE 1976', 'Fairchild 2010'}** Aliases: - 'astm2008': 'ASTM D1535' - 'cie1976': 'CIE 1976' """ LUMINANCE_METHODS['astm2008'] = (LUMINANCE_METHODS['ASTM D1535']) LUMINANCE_METHODS['cie1976'] = (LUMINANCE_METHODS['CIE 1976'])
[docs]def luminance(LV, method='CIE 1976', **kwargs): """ Returns the *luminance* :math:`Y` of given *Lightness* :math:`L^*` or given *Munsell* value :math:`V`. Parameters ---------- LV : numeric or array_like *Lightness* :math:`L^*` or *Munsell* value :math:`V`. method : unicode, optional **{'CIE 1976', 'Newhall 1943', 'ASTM D1535', 'Fairchild 2010', 'Fairchild 2011'}**, Computation method. Other Parameters ---------------- Y_n : numeric or array_like, optional {:func:`colour.colorimetry.luminance_CIE1976`}, White reference *luminance* :math:`Y_n`. epsilon : numeric or array_like, optional {:func:`colour.colorimetry.lightness_Fairchild2010`, :func:`colour.colorimetry.lightness_Fairchild2011`}, :math:`\\epsilon` exponent. Returns ------- numeric or array_like *luminance* :math:`Y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``LV`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``Y`` | [0, 100] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`ASTMInternational2008a`, :cite:`CIETC1-482004m`, :cite:`Fairchild2010`, :cite:`Fairchild2011`, :cite:`Newhall1943a`, :cite:`Wikipedia2001b`, :cite:`Wyszecki2000bd` Examples -------- >>> luminance(41.527875844653451) # doctest: +ELLIPSIS 12.1972253... >>> luminance(41.527875844653451, Y_n=100) # doctest: +ELLIPSIS 12.1972253... >>> luminance(42.51993072812094, Y_n=95) # doctest: +ELLIPSIS 12.1972253... >>> luminance(4.08244375 * 10, method='Newhall 1943') ... # doctest: +ELLIPSIS 12.5500788... >>> luminance(4.08244375 * 10, method='ASTM D1535') ... # doctest: +ELLIPSIS 12.2363426... >>> luminance(29.829510892279330, epsilon=0.710, method='Fairchild 2011') ... # doctest: +ELLIPSIS 12.1972253... """ function = LUMINANCE_METHODS[method] domain_range_reference = get_domain_range_scale() == 'reference' domain_1 = (luminance_Fairchild2010, luminance_Fairchild2011) domain_10 = (luminance_Newhall1943, luminance_ASTMD1535) if function in domain_10 and domain_range_reference: LV /= 10 Y_V = function(LV, **filter_kwargs(function, **kwargs)) if function in domain_1 and domain_range_reference: Y_V *= 100 return Y_V