Source code for colour.models.rgb.transfer_functions.itut_h_273

"""
Recommendation ITU-T H.273 Transfer Characteristics
===================================================

Defines the *Recommendation ITU-T H.273* transfer functions that do not belong
in another specification or standard, or have been modified for inclusion:

-   :func:`colour.models.oetf_H273_Log`
-   :func:`colour.models.oetf_inverse_H273_Log`
-   :func:`colour.models.oetf_H273_LogSqrt`
-   :func:`colour.models.oetf_inverse_H273_LogSqrt`
-   :func:`colour.models.oetf_H273_IEC61966_2`
-   :func:`colour.models.oetf_inverse_H273_IEC61966_2`
-   :func:`colour.models.eotf_H273_ST428_1`
-   :func:`colour.models.eotf_inverse_H273_ST428_1`

References
----------
-   :cite:`InternationalTelecommunicationUnion2021` : International
    Telecommunication Union. (2021). Recommendation ITU-T H.273 -
    Coding-independent code points for video signal type identification.
    https://www.itu.int/rec/T-REC-H.273-202107-I/en
-   :cite:`SocietyofMotionPictureandTelevisionEngineers2019` : Society of
    Motion Picture and Television Engineers. (2019). ST 428-1:2019 - D-Cinema
    Distribution Master — Image Characteristic. doi:10.5594/SMPTE.ST428-1.2019
"""

import numpy as np

from colour.algebra import spow
from colour.models.rgb.transfer_functions import (
    eotf_inverse_DCDM,
    eotf_DCDM,
    eotf_inverse_sRGB,
    eotf_sRGB,
)
from colour.utilities import (
    as_float,
    as_float_array,
    from_range_1,
    to_domain_1,
)

__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 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__ = [
    "oetf_H273_Log",
    "oetf_inverse_H273_Log",
    "oetf_H273_LogSqrt",
    "oetf_inverse_H273_LogSqrt",
    "oetf_H273_IEC61966_2",
    "oetf_inverse_H273_IEC61966_2",
    "eotf_inverse_H273_ST428_1",
    "eotf_H273_ST428_1",
]


[docs]def oetf_H273_Log(L_c): """ Define *Recommendation ITU-T H.273* opto-electronic transfer function (OETF) for logarithmic encoding (100:1 range). Parameters ---------- L_c Scene *Luminance* :math:`L_c`. Returns ------- :class:`numpy.ndarray` Corresponding electrical signal :math:`V`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2021` Warnings -------- - The function is clamped to domain [0.01, np.inf]. Examples -------- >>> oetf_H273_Log(0.18) # doctest: +ELLIPSIS 0.6276362525516... >>> oetf_H273_Log(0.01) # doctest: +ELLIPSIS 0.0 >>> oetf_H273_Log(0.001) # doctest: +ELLIPSIS 0.0 >>> oetf_H273_Log(1.0) # doctest: +ELLIPSIS 1.0 """ L_c = to_domain_1(L_c) V = np.where( L_c >= 0.01, # L_c in [0.01, 1] range 1 + np.log10(L_c) / 2, # L_c in [0, 0.01] range 0, ) return as_float(from_range_1(V))
[docs]def oetf_inverse_H273_Log(V): """ Define *Recommendation ITU-T H.273* inverse-opto-electronic transfer function (OETF) for logarithmic encoding (100:1 range). Parameters ---------- V Electrical signal :math:`V`. Returns ------- :class:`numpy.ndarray` Corresponding scene *Luminance* :math:`L_c`. Notes ----- +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2021` Warnings -------- - The function is clamped to domain [:func:`colour.models.oetf_H273_Log` (0.01), np.inf]. Examples -------- >>> oetf_inverse_H273_Log(0.6276362525516) # doctest: +ELLIPSIS 0.17999999... >>> oetf_inverse_H273_Log(0.0) # doctest: +ELLIPSIS 0.01 >>> oetf_inverse_H273_Log(1.0) # doctest: +ELLIPSIS 1.0 """ V = to_domain_1(V) L_c = np.where( V >= oetf_H273_Log(0.01), # L_c in [0.01, 1] range spow(10, (V - 1) * 2), # L_c in [0, 0.01] range 0, ) return as_float(from_range_1(L_c))
[docs]def oetf_H273_LogSqrt(L_c): """ Define *Recommendation ITU-T H.273* opto-electronic transfer function (OETF) for logarithmic encoding (100\\*Sqrt(10):1 range). Parameters ---------- L_c Scene *Luminance* :math:`L_c`. Returns ------- :class:`numpy.ndarray` Corresponding electrical signal :math:`V`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2021` Warnings -------- - The function is clamped to domain [:func:`colour.models.oetf_H273_LogSqrt` (sqrt(10) / 1000), np.inf]. Examples -------- >>> oetf_H273_LogSqrt(0.18) # doctest: +ELLIPSIS 0.702109002041... >>> oetf_H273_LogSqrt(0.003162277660168) # doctest: +ELLIPSIS 0.0 >>> oetf_H273_LogSqrt(0.0001) # doctest: +ELLIPSIS 0.0 >>> oetf_H273_LogSqrt(1.0) # doctest: +ELLIPSIS 1.0 """ L_c = to_domain_1(L_c) V = np.where( L_c >= np.sqrt(10) / 1000, # L_c in [sqrt(10)/1000, 1] range 1 + np.log10(L_c) / 2.5, # L_c in [0, sqrt(10)/1000] range 0, ) return as_float(from_range_1(V))
[docs]def oetf_inverse_H273_LogSqrt(V): """ Define *Recommendation ITU-T H.273* inverse-opto-electronic transfer function (OETF) for logarithmic encoding (100\\*Sqrt(10):1 range). Parameters ---------- V Electrical signal :math:`V`. Returns ------- :class:`numpy.ndarray` Corresponding scene *Luminance* :math:`L_c`. Notes ----- +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`InternationalTelecommunicationUnion2021` Warnings -------- - The function is clamped to domain [sqrt(10) / 1000, np.inf]. Examples -------- >>> oetf_inverse_H273_LogSqrt(0.702109002041) # doctest: +ELLIPSIS 0.1799999999... >>> oetf_inverse_H273_LogSqrt(0.0) # doctest: +ELLIPSIS 0.00316227766... >>> oetf_inverse_H273_LogSqrt(1.0) # doctest: +ELLIPSIS 1.0 """ V = to_domain_1(V) L_c = np.where( V >= oetf_H273_LogSqrt(np.sqrt(10) / 1000), # L_c in [sqrt(10)/1000, 1] range spow(10, (V - 1) * 2.5), # L_c in [0, sqrt(10)/1000] range 0, ) return as_float(from_range_1(L_c))
[docs]def oetf_H273_IEC61966_2(L_c): """ Define *Recommendation ITU-T H.273* opto-electronic transfer function (OETF) for *IEC 61966-2* family of transfer functions (*2-1 sRGB*, *2-1 sYCC*, *2-4 xvYCC*). Parameters ---------- L_c Scene *Luminance* :math:`L_c`. Returns ------- :class:`numpy.ndarray` Corresponding electrical signal :math:`V`. Notes ----- Usage in :cite:`InternationalTelecommunicationUnion2021` is as follows: - For *IEC 61966-2-1 sRGB (MatrixCoefficients=0)*, the function is only defined for :math:`L_c` in [0-1] range. - For *IEC 61966-2-1 sYCC (MatrixCoefficients=5)* and *IEC 61966-2-4 xvYCC*, the function is defined for any real-valued :math:`L_c`. +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- - :cite:`InternationalTelecommunicationUnion2021` Examples -------- >>> oetf_H273_IEC61966_2(0.18) # doctest: +ELLIPSIS 0.4613561295004... >>> oetf_H273_IEC61966_2(-0.18) # doctest: +ELLIPSIS -0.4613561295004... """ V = np.where( as_float_array(L_c) >= 0, eotf_inverse_sRGB(L_c), -eotf_inverse_sRGB(-L_c), ) return as_float(V)
[docs]def oetf_inverse_H273_IEC61966_2(V): """ Define *Recommendation ITU-T H.273* inverse opto-electronic transfer function (OETF) for *IEC 61966-2* family of transfer functions (*2-1 sRGB*, *2-1 sYCC*, *2-4 xvYCC*). Parameters ---------- V Electrical signal :math:`V`. Returns ------- :class:`numpy.ndarray` Corresponding scene luminance :math:`L_c`. Notes ----- Usage in :cite:`InternationalTelecommunicationUnion2021` is as follows: - For *IEC 61966-2-1 sRGB (MatrixCoefficients=0)*, the function is only defined for :math:`L_c` in [0-1] range. - For *IEC 61966-2-1 sYCC (MatrixCoefficients=5)* and *IEC 61966-2-4 xvYCC*, the function is defined for any real-valued :math:`L_c`. +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_c`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- - :cite:`InternationalTelecommunicationUnion2021` Examples -------- >>> oetf_inverse_H273_IEC61966_2(0.461356129500) # doctest: +ELLIPSIS 0.1799999999... >>> oetf_inverse_H273_IEC61966_2(-0.461356129500) # doctest: +ELLIPSIS -0.1799999999... """ L_c = np.where( as_float_array(V) >= 0, eotf_sRGB(V), -eotf_sRGB(-V), ) return as_float(L_c)
[docs]def eotf_inverse_H273_ST428_1(L_o): """ Define *Recommendation ITU-T H.273* inverse electro-optical transfer function (EOTF) for *SMPTE ST 428-1 (2019)*. Parameters ---------- L_o Output display *Luminance* :math:`L_o` of the image. Returns ------- :class:`numpy.ndarray` Corresponding electrical signal :math:`V`. Notes ----- - The function given in :cite:`InternationalTelecommunicationUnion2021` multiplies :math:`L_o` by 48 contrary to what is given in :cite:`SocietyofMotionPictureandTelevisionEngineers2019` and :func:`colour.models.eotf_inverse_DCDM`. +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_o`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- - :cite:`InternationalTelecommunicationUnion2021`, :cite:`SocietyofMotionPictureandTelevisionEngineers2019` Examples -------- >>> eotf_inverse_H273_ST428_1(0.18) # doctest: +ELLIPSIS 0.5000483... """ L_o = to_domain_1(L_o) return as_float(from_range_1(eotf_inverse_DCDM(L_o * 48)))
[docs]def eotf_H273_ST428_1(V): """ Define the *SMPTE ST 428-1 (2019)* electro-optical transfer function (EOTF). Parameters ---------- V Electrical signal :math:`V`. Returns ------- :class:`numpy.ndarray` Corresponding output display *Luminance* :math:`L_o` of the image. Notes ----- - The function given in :cite:`InternationalTelecommunicationUnion2021` divides :math:`L_o` by 48 contrary to what is given in :cite:`SocietyofMotionPictureandTelevisionEngineers2019` and :func:`colour.models.eotf_DCDM`. +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``V`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``L_o`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- - :cite:`InternationalTelecommunicationUnion2021`, :cite:`SocietyofMotionPictureandTelevisionEngineers2019` Examples -------- >>> eotf_H273_ST428_1(0.5000483377172) # doctest: +ELLIPSIS 0.1799999... """ V = to_domain_1(V) return as_float(from_range_1(eotf_DCDM(V) / 48))