Source code for colour.models.rgb.transfer_functions.itur_bt_1886

# -*- coding: utf-8 -*-
"""
ITU-R BT.1886
=============

Defines the *Recommendation ITU-R BT.1886* electro-optical transfer function
(EOTF / EOCF) and its inverse:

-   :func:`colour.models.eotf_inverse_BT1886`
-   :func:`colour.models.eotf_BT1886`

References
----------
-   :cite:`InternationalTelecommunicationUnion2011h` : International
    Telecommunication Union. (2011). Recommendation ITU-R BT.1886 - Reference
    electro-optical transfer function for flat panel displays used in HDTV
    studio production BT Series Broadcasting service.
    https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.1886-0-201103-I!!PDF-E.pdf
"""

import numpy as np

from colour.utilities import 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_BT1886', 'eotf_BT1886']


[docs]def eotf_inverse_BT1886(L, L_B=0, L_W=1): """ Defines *Recommendation ITU-R BT.1886* inverse electro-optical transfer function (EOTF / EOCF). Parameters ---------- L : numeric or array_like Screen luminance in :math:`cd/m^2`. L_B : numeric, optional Screen luminance for black. L_W : numeric, optional Screen luminance for white. Returns ------- numeric or ndarray Input video signal level (normalised, black at :math:`V = 0`, to white at :math:`V = 1`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2011h` Examples -------- >>> eotf_inverse_BT1886(0.11699185725296059) # doctest: +ELLIPSIS 0.4090077... """ L = to_domain_1(L) gamma = 2.40 gamma_d = 1 / gamma n = L_W ** gamma_d - L_B ** gamma_d a = n ** gamma b = L_B ** gamma_d / n V = (L / a) ** gamma_d - b return from_range_1(V)
[docs]def eotf_BT1886(V, L_B=0, L_W=1): """ Defines *Recommendation ITU-R BT.1886* electro-optical transfer function (EOTF / EOCF). Parameters ---------- V : numeric or array_like Input video signal level (normalised, black at :math:`V = 0`, to white at :math:`V = 1`. For content mastered per *Recommendation ITU-R BT.709*, 10-bit digital code values :math:`D` map into values of :math:`V` per the following equation: :math:`V = (D-64)/876` L_B : numeric, optional Screen luminance for black. L_W : numeric, optional Screen luminance for white. Returns ------- numeric or ndarray Screen luminance in :math:`cd/m^2`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2011h` Examples -------- >>> eotf_BT1886(0.409007728864150) # doctest: +ELLIPSIS 0.1169918... """ V = to_domain_1(V) gamma = 2.40 gamma_d = 1 / gamma n = L_W ** gamma_d - L_B ** gamma_d a = n ** gamma b = L_B ** gamma_d / n L = a * np.maximum(V + b, 0) ** gamma return from_range_1(L)