# -*- 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`
See Also
--------
`RGB Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/rgb.ipynb>`_
References
----------
- :cite:`SocietyofMotionPictureandTelevisionEngineers1999b` : Society of
Motion Picture and Television Engineers. (1999). ANSI/SMPTE 240M-1995 -
Signal Parameters - 1125-Line High-Definition Production Systems. Retrieved
from http://car.france3.mars.free.fr/HD/INA- 26 jan 06/\
SMPTE normes et confs/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) 2013-2019 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__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))