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

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
Viper Log Encodings
===================

Defines the *Viper Log* encoding:

-   :func:`log_encoding_ViperLog`
-   :func:`log_decoding_ViperLog`

See Also
--------
`RGB Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/rgb.ipynb>`_

References
----------
.. [1]  Sony Imageworks. (2012). make.py. Retrieved November 27, 2014, from
        https://github.com/imageworks/OpenColorIO-Configs/\
blob/master/nuke-default/make.py
"""

from __future__ import division, unicode_literals

import numpy as np

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2017 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'

__all__ = ['log_encoding_ViperLog',
           'log_decoding_ViperLog']


[docs]def log_encoding_ViperLog(x): """ Defines the *Viper Log* 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`. Examples -------- >>> log_encoding_ViperLog(0.18) # doctest: +ELLIPSIS 0.6360080... """ x = np.asarray(x) return (1023 + 500 * np.log10(x)) / 1023
[docs]def log_decoding_ViperLog(y): """ Defines the *Viper Log* 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`. Examples -------- >>> log_decoding_ViperLog(0.636008067010413) # doctest: +ELLIPSIS 0.1799999... """ y = np.asarray(y) return 10 ** ((1023 * y - 1023) / 500)