Source code for colour.models.rgb.transfer_functions.smpte_240m

# -*- coding: utf-8 -*-
"""
SMPTE 240M
==========

Defines *SMPTE 240M* opto-electrical transfer function (OETF / OECF) and
electro-optical transfer function (EOTF / EOCF):

-   :func:`colour.models.oetf_SMPTE240M`
-   :func:`colour.models.eotf_SMPTE240M`

References
----------
-   :cite:`SocietyofMotionPictureandTelevisionEngineers1999b` : Society of
    Motion Picture and Television Engineers. (1999). ANSI/SMPTE 240M-1995 -
    Signal Parameters - 1125-Line High-Definition Production Systems (pp. 1-7).
    http://car.france3.mars.free.fr/HD/INA-%2026%20jan%2006/\
SMPTE%20normes%20et%20confs/s240m.pdf
"""

from __future__ import division, unicode_literals

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) 2013-2020 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = '[email protected]'
__status__ = 'Production'

__all__ = ['oetf_SMPTE240M', 'eotf_SMPTE240M']


[docs]def oetf_SMPTE240M(L_c): """ Defines *SMPTE 240M* opto-electrical transfer function (OETF / OECF). Parameters ---------- L_c : numeric or array_like Light input :math:`L_c` to the reference camera normalised to the system reference white. Returns ------- numeric or ndarray Video signal output :math:`V_c` of the reference camera normalised to the system reference white. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SocietyofMotionPictureandTelevisionEngineers1999b` Examples -------- >>> oetf_SMPTE240M(0.18) # doctest: +ELLIPSIS 0.4022857... """ L_c = to_domain_1(L_c) V_c = np.where(L_c < 0.0228, 4 * L_c, 1.1115 * spow(L_c, 0.45) - 0.1115) return as_float(from_range_1(V_c))
[docs]def eotf_SMPTE240M(V_r): """ Defines *SMPTE 240M* electro-optical transfer function (EOTF / EOCF). Parameters ---------- V_r : numeric or array_like Video signal level :math:`V_r` driving the reference reproducer normalised to the system reference white. Returns ------- numeric or ndarray Light output :math:`L_r` from the reference reproducer normalised to the system reference white. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SocietyofMotionPictureandTelevisionEngineers1999b` Examples -------- >>> eotf_SMPTE240M(0.402285796753870) # doctest: +ELLIPSIS 0.1... """ V_r = to_domain_1(V_r) with domain_range_scale('ignore'): L_r = np.where( V_r < oetf_SMPTE240M(0.0228), V_r / 4, spow((V_r + 0.1115) / 1.1115, 1 / 0.45), ) return as_float(from_range_1(L_r))