Source code for colour.models.rgb.transfer_functions.srgb

# -*- coding: utf-8 -*-
"""
sRGB
====

Defines the *sRGB* electro-optical transfer function (EOTF / EOCF) and its
inverse:

-   :func:`colour.models.eotf_inverse_sRGB`
-   :func:`colour.models.eotf_sRGB`

References
----------
-   :cite:`InternationalElectrotechnicalCommission1999a` : International
    Electrotechnical Commission. (1999). IEC 61966-2-1:1999 - Multimedia
    systems and equipment - Colour measurement and management - Part 2-1:
    Colour management - Default RGB colour space - sRGB (p. 51).
    https://webstore.iec.ch/publication/6169
-   :cite:`InternationalTelecommunicationUnion2015i` : International
    Telecommunication Union. (2015). Recommendation ITU-R BT.709-6 - Parameter
    values for the HDTV standards for production and international programme
    exchange BT Series Broadcasting service (pp. 1-32).
    https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.709-6-201506-I!!PDF-E.pdf
"""

import numpy as np

from colour.algebra import spow
from colour.utilities import (as_float, domain_range_scale, from_range_1,
                              to_domain_1)

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2021 - 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__ = ['eotf_inverse_sRGB', 'eotf_sRGB']


[docs]def eotf_inverse_sRGB(L): """ Defines the *IEC 61966-2-1:1999* *sRGB* inverse electro-optical transfer function (EOTF / EOCF). Parameters ---------- L : numeric or array_like *Luminance* :math:`L` of the image. Returns ------- numeric or ndarray Corresponding electrical signal :math:`V`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalElectrotechnicalCommission1999a`, :cite:`InternationalTelecommunicationUnion2015i` Examples -------- >>> eotf_inverse_sRGB(0.18) # doctest: +ELLIPSIS 0.4613561... """ L = to_domain_1(L) V = np.where(L <= 0.0031308, L * 12.92, 1.055 * spow(L, 1 / 2.4) - 0.055) return as_float(from_range_1(V))
[docs]def eotf_sRGB(V): """ Defines the *IEC 61966-2-1:1999* *sRGB* electro-optical transfer function (EOTF / EOCF). Parameters ---------- V : numeric or array_like Electrical signal :math:`V`. Returns ------- numeric or ndarray Corresponding *luminance* :math:`L` of the image. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalElectrotechnicalCommission1999a`, :cite:`InternationalTelecommunicationUnion2015i` Examples -------- >>> eotf_sRGB(0.461356129500442) # doctest: +ELLIPSIS 0.1... """ V = to_domain_1(V) with domain_range_scale('ignore'): L = np.where( V <= eotf_inverse_sRGB(0.0031308), V / 12.92, spow((V + 0.055) / 1.055, 2.4), ) return as_float(from_range_1(L))