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

# -*- coding: utf-8 -*-
"""
Pivoted Log Encoding
====================

Defines the *Pivoted Log* encoding:

-   :func:`colour.models.log_encoding_PivotedLog`
-   :func:`colour.models.log_decoding_PivotedLog`

References
----------
-   :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.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__ = ['log_encoding_PivotedLog', 'log_decoding_PivotedLog']


[docs]def log_encoding_PivotedLog(x, log_reference=445, linear_reference=0.18, negative_gamma=0.6, density_per_code_value=0.002): """ Defines the *Josh Pines* style *Pivoted Log* log encoding curve / opto-electronic transfer function. Parameters ---------- x : numeric or array_like Linear data :math:`x`. log_reference : numeric or array_like Log reference. linear_reference : numeric or array_like Linear reference. negative_gamma : numeric or array_like Negative gamma. density_per_code_value : numeric or array_like Density per code value. 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_PivotedLog(0.18) # doctest: +ELLIPSIS 0.4349951... """ x = to_domain_1(x) y = ((log_reference + np.log10(x / linear_reference) / (density_per_code_value / negative_gamma)) / 1023) return from_range_1(y)
[docs]def log_decoding_PivotedLog(y, log_reference=445, linear_reference=0.18, negative_gamma=0.6, density_per_code_value=0.002): """ Defines the *Josh Pines* style *Pivoted Log* log decoding curve / electro-optical transfer function. Parameters ---------- y : numeric or array_like Non-linear data :math:`y`. log_reference : numeric or array_like Log reference. linear_reference : numeric or array_like Linear reference. negative_gamma : numeric or array_like Negative gamma. density_per_code_value : numeric or array_like Density per code value. 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_PivotedLog(0.434995112414467) # doctest: +ELLIPSIS 0.1... """ y = to_domain_1(y) x = (10 ** ((y * 1023 - log_reference) * (density_per_code_value / negative_gamma)) * linear_reference) return from_range_1(x)