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

# -*- coding: utf-8 -*-
"""
RED Log Encodings
=================

Defines the *RED* log encodings:

-   :func:`colour.models.log_encoding_REDLog`
-   :func:`colour.models.log_decoding_REDLog`
-   :func:`colour.models.log_encoding_REDLogFilm`
-   :func:`colour.models.log_decoding_REDLogFilm`
-   :func:`colour.models.log_encoding_Log3G10_v1`
-   :func:`colour.models.log_decoding_Log3G10_v1`
-   :func:`colour.models.log_encoding_Log3G10_v2`
-   :func:`colour.models.log_decoding_Log3G10_v2`
-   :func:`colour.models.log_encoding_Log3G10_v3`
-   :func:`colour.models.log_decoding_Log3G10_v3`
-   :attr:`colour.models.LOG3G10_ENCODING_METHODS`
-   :func:`colour.models.log_encoding_Log3G10`
-   :attr:`colour.models.LOG3G10_DECODING_METHODS`
-   :func:`colour.models.log_decoding_Log3G10`
-   :func:`colour.models.log_encoding_Log3G12`
-   :func:`colour.models.log_decoding_Log3G12`

References
----------
-   :cite:`Nattress2016a` : Nattress, G. (2016). Private Discussion with Shaw,
    N.
-   :cite:`REDDigitalCinema2017` : RED Digital Cinema. (2017). White Paper on
    REDWideGamutRGB and Log3G10. Retrieved January 16, 2021, from
    https://www.red.com/download/white-paper-on-redwidegamutrgb-and-log3g10
-   :cite:`SonyImageworks2012a` : Sony Imageworks. (2012). make.py. Retrieved
    November 27, 2014, from
    https://github.com/imageworks/OpenColorIO-Configs/blob/master/\
nuke-default/make.py
"""

import numpy as np

from colour.models.rgb.transfer_functions import (log_encoding_Cineon,
                                                  log_decoding_Cineon)

from colour.utilities import (CaseInsensitiveMapping, from_range_1,
                              to_domain_1, as_numeric, validate_method)

__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__ = [
    'log_encoding_REDLog', 'log_decoding_REDLog', 'log_encoding_REDLogFilm',
    'log_decoding_REDLogFilm', 'log_encoding_Log3G10_v1',
    'log_decoding_Log3G10_v1', 'log_encoding_Log3G10_v2',
    'log_decoding_Log3G10_v2', 'log_encoding_Log3G10_v3',
    'log_decoding_Log3G10_v3', 'LOG3G10_ENCODING_METHODS',
    'log_encoding_Log3G10', 'LOG3G10_DECODING_METHODS', 'log_decoding_Log3G10',
    'log_encoding_Log3G12', 'log_decoding_Log3G12'
]


[docs]def log_encoding_REDLog(x, black_offset=10 ** ((0 - 1023) / 511)): """ Defines the *REDLog* log encoding curve / opto-electronic transfer function. Parameters ---------- x : numeric or array_like Linear data :math:`x`. black_offset : numeric or array_like Black offset. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SonyImageworks2012a` Examples -------- >>> log_encoding_REDLog(0.18) # doctest: +ELLIPSIS 0.6376218... """ x = to_domain_1(x) y = (1023 + 511 * np.log10(x * (1 - black_offset) + black_offset)) / 1023 return from_range_1(y)
[docs]def log_decoding_REDLog(y, black_offset=10 ** ((0 - 1023) / 511)): """ Defines the *REDLog* log decoding curve / electro-optical transfer function. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. black_offset : numeric or array_like Black offset. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SonyImageworks2012a` Examples -------- >>> log_decoding_REDLog(0.637621845988175) # doctest: +ELLIPSIS 0.1... """ y = to_domain_1(y) x = ((10 ** ((1023 * y - 1023) / 511)) - black_offset) / (1 - black_offset) return from_range_1(x)
[docs]def log_encoding_REDLogFilm(x, black_offset=10 ** ((95 - 685) / 300)): """ Defines the *REDLogFilm* log encoding curve / opto-electronic transfer function. Parameters ---------- x : numeric or array_like Linear data :math:`x`. black_offset : numeric or array_like Black offset. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SonyImageworks2012a` Examples -------- >>> log_encoding_REDLogFilm(0.18) # doctest: +ELLIPSIS 0.4573196... """ return log_encoding_Cineon(x, black_offset)
[docs]def log_decoding_REDLogFilm(y, black_offset=10 ** ((95 - 685) / 300)): """ Defines the *REDLogFilm* log decoding curve / electro-optical transfer function. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. black_offset : numeric or array_like Black offset. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`SonyImageworks2012a` Examples -------- >>> log_decoding_REDLogFilm(0.457319613085418) # doctest: +ELLIPSIS 0.1799999... """ return log_decoding_Cineon(y, black_offset)
def log_encoding_Log3G10_v1(x): """ Defines the *Log3G10* *v1* log encoding curve / opto-electronic transfer function, the curve used in *REDCINE-X PRO Beta 42* and *Resolve 12.5.2*. Parameters ---------- x : numeric or array_like Linear data :math:`x`. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a` Examples -------- >>> log_encoding_Log3G10_v1(0.18) # doctest: +ELLIPSIS 0.3333336... """ x = to_domain_1(x) y = np.sign(x) * 0.222497 * np.log10((np.abs(x) * 169.379333) + 1) return from_range_1(y) def log_decoding_Log3G10_v1(y): """ Defines the *Log3G10* *v1* log decoding curve / electro-optical transfer function, the curve used in *REDCINE-X PRO Beta 42* and *Resolve 12.5.2*. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a` Examples -------- >>> log_decoding_Log3G10_v1(1.0 / 3) # doctest: +ELLIPSIS 0.1799994... """ y = to_domain_1(y) x = (np.sign(y) * (10.0 ** (np.abs(y) / 0.222497) - 1) / 169.379333) return from_range_1(x) def log_encoding_Log3G10_v2(x): """ Defines the *Log3G10* *v2* log encoding curve / opto-electronic transfer function, the current curve in *REDCINE-X PRO*. Parameters ---------- x : numeric or array_like Linear data :math:`x`. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a` Examples -------- >>> log_encoding_Log3G10_v2(0.0) # doctest: +ELLIPSIS 0.0915514... """ x = to_domain_1(x) y = (np.sign(x + 0.01) * 0.224282 * np.log10((np.abs(x + 0.01) * 155.975327) + 1)) return from_range_1(y) def log_decoding_Log3G10_v2(y): """ Defines the *Log3G10* *v2* log decoding curve / electro-optical transfer function, the current curve in *REDCINE-X PRO*. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a` Examples -------- >>> log_decoding_Log3G10_v2(1.0) # doctest: +ELLIPSIS 184.3223476... """ y = to_domain_1(y) x = (np.sign(y) * (10.0 ** (np.abs(y) / 0.224282) - 1) / 155.975327) - 0.01 return from_range_1(x) def log_encoding_Log3G10_v3(x): """ Defines the *Log3G10* *v3* log encoding curve / opto-electronic transfer function, the curve described in the RedLog3G10 Whitepaper. Parameters ---------- x : numeric or array_like Linear data :math:`x`. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`REDDigitalCinema2017` Examples -------- >>> log_encoding_Log3G10_v3(0.0) # doctest: +ELLIPSIS 0.09155148... """ a = 0.224282 b = 155.975327 c = 0.01 g = 15.1927 x = to_domain_1(x) x = x + c y = np.where(x < 0.0, x * g, np.sign(x) * a * np.log10((np.abs(x) * b) + 1.0)) return as_numeric(from_range_1(y)) def log_decoding_Log3G10_v3(y): """ Defines the *Log3G10* *v3* log decoding curve / electro-optical transfer function, the curve described in the RedLog3G10 whitepaper. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`REDDigitalCinema2017` Examples -------- >>> log_decoding_Log3G10_v3(1.0) # doctest: +ELLIPSIS 184.32234764... """ a = 0.224282 b = 155.975327 c = 0.01 g = 15.1927 y = to_domain_1(y) x = np.where(y < 0.0, (y / g) - c, np.sign(y) * (10 ** (np.abs(y) / a) - 1.0) / b - c) return as_numeric(from_range_1(x)) LOG3G10_ENCODING_METHODS = CaseInsensitiveMapping({ 'v1': log_encoding_Log3G10_v1, 'v2': log_encoding_Log3G10_v2, 'v3': log_encoding_Log3G10_v3, }) LOG3G10_ENCODING_METHODS.__doc__ = """ Supported *Log3G10* log encoding curve / opto-electronic transfer function methods. References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` LOG3G10_ENCODING_METHODS : CaseInsensitiveMapping **{'v1', 'v2', 'v3'}** """
[docs]def log_encoding_Log3G10(x, method='v3'): """ Defines the *Log3G10* log encoding curve / opto-electronic transfer function. Parameters ---------- x : numeric or array_like Linear data :math:`x`. method : unicode, optional **{'v1', 'v2', 'v3'}**, Computation method. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ - The *Log3G10* *v1* log encoding curve is the one used in *REDCINE-X Beta 42*. *Resolve 12.5.2* also uses the *v1* curve. *RED* is planning to use the *Log3G10* *v2* log encoding curve in the release version of the *RED SDK*. - The intent of the *Log3G10* *v1* log encoding curve is that zero maps to zero, 0.18 maps to 1/3, and 10 stops above 0.18 maps to 1.0. The name indicates this in a similar way to the naming conventions of *Sony HyperGamma* curves. The constants used in the functions do not in fact quite hit these values, but rather than use corrected constants, the functions here use the official *RED* values, in order to match the output of the *RED SDK*. For those interested, solving for constants which exactly hit 1/3 and 1.0 yields the following values:: B = 25 * (np.sqrt(4093.0) - 3) / 9 A = 1 / np.log10(B * 184.32 + 1) where the function takes the form:: Log3G10(x) = A * np.log10(B * x + 1) Similarly for *Log3G12*, the values which hit exactly 1/3 and 1.0 are:: B = 25 * (np.sqrt(16381.0) - 3) / 9 A = 1 / np.log10(B * 737.28 + 1) References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` Examples -------- >>> log_encoding_Log3G10(0.0) # doctest: +ELLIPSIS 0.09155148... >>> log_encoding_Log3G10(0.18, method='v1') # doctest: +ELLIPSIS 0.3333336... """ method = validate_method(method, LOG3G10_ENCODING_METHODS) return LOG3G10_ENCODING_METHODS[method](x)
LOG3G10_DECODING_METHODS = CaseInsensitiveMapping({ 'v1': log_decoding_Log3G10_v1, 'v2': log_decoding_Log3G10_v2, 'v3': log_decoding_Log3G10_v3, }) LOG3G10_DECODING_METHODS.__doc__ = """ Supported *Log3G10* log decoding curve / electro-optical transfer function methods. References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` LOG3G10_DECODING_METHODS : CaseInsensitiveMapping **{'v1', 'v2', 'v3'}** """
[docs]def log_decoding_Log3G10(y, method='v3'): """ Defines the *Log3G10* log decoding curve / electro-optical transfer function. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. method : unicode, optional **{'v1', 'v2', 'v3'}**, Computation method. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` Examples -------- >>> log_decoding_Log3G10(1.0) # doctest: +ELLIPSIS 184.3223476... >>> log_decoding_Log3G10(1.0 / 3, method='v1') # doctest: +ELLIPSIS 0.1799994... """ method = validate_method(method, LOG3G10_DECODING_METHODS) return LOG3G10_DECODING_METHODS[method](y)
[docs]def log_encoding_Log3G12(x): """ Defines the *Log3G12* log encoding curve / opto-electronic transfer function. Parameters ---------- x : numeric or array_like Linear data :math:`x`. Returns ------- numeric or ndarray Non-linear data :math:`y`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` Examples -------- >>> log_encoding_Log3G12(0.18) # doctest: +ELLIPSIS 0.3333326... """ x = to_domain_1(x) y = np.sign(x) * 0.184904 * np.log10((np.abs(x) * 347.189667) + 1) return from_range_1(y)
[docs]def log_decoding_Log3G12(y): """ Defines the *Log3G12* log decoding curve / electro-optical transfer function. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. Returns ------- numeric or ndarray Linear data :math:`x`. Notes ----- +------------+-----------------------+---------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``y`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ +------------+-----------------------+---------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+===============+ | ``x`` | [0, 1] | [0, 1] | +------------+-----------------------+---------------+ References ---------- :cite:`Nattress2016a`, :cite:`REDDigitalCinema2017` Examples -------- >>> log_decoding_Log3G12(1.0 / 3) # doctest: +ELLIPSIS 0.1800015... """ y = to_domain_1(y) x = np.sign(y) * (10.0 ** (np.abs(y) / 0.184904) - 1) / 347.189667 return from_range_1(x)