#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
:math:`IC_TC_P` Colour Encoding
===============================
Defines the :math:`IC_TC_P` colour encoding related transformations:
- :func:`RGB_to_ICTCP`
- :func:`ICTCP_to_RGB`
See Also
--------
`ICTCP Colourspace Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/ictcp.ipynb>`_
References
----------
.. [1] Dolby. (2016). WHAT IS ICTCP? - INTRODUCTION. Retrieved from
https://www.dolby.com/us/en/technologies/dolby-vision/\
ICtCp-white-paper.pdf
.. [2] Lu, T., Pu, F., Yin, P., Chen, T., Husak, W., Pytlarz, J., … Su, G.-M.
(2016). ICTCP Colour Space and Its Compression Performance for High
Dynamic Range and Wide Colour Gamut Video Distribution. ZTE
Communications, 14(1), 32–38. doi:10.3969/j.
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.models.rgb.transfer_functions import oetf_ST2084, eotf_ST2084
from colour.utilities import dot_vector
__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__ = [
'ICTCP_RGB_TO_LMS_MATRIX', 'ICTCP_LMS_TO_RGB_MATRIX',
'ICTCP_LMS_P_TO_ICTCP_MATRIX', 'ICTCP_ICTCP_TO_LMS_P_MATRIX',
'RGB_to_ICTCP', 'ICTCP_to_RGB'
]
ICTCP_RGB_TO_LMS_MATRIX = np.array(
[[1688, 2146, 262],
[683, 2951, 462],
[99, 309, 3688]]) / 4096 # yapf: disable
"""
*Rec. 2020* colourspace to normalised cone responses matrix.
ICTCP_RGB_TO_LMS_MATRIX : array_like, (3, 3)
"""
ICTCP_LMS_TO_RGB_MATRIX = np.linalg.inv(ICTCP_RGB_TO_LMS_MATRIX)
"""
:math:`IC_TC_P` colourspace normalised cone responses to *Rec. 2020*
colourspace matrix.
ICTCP_LMS_TO_RGB_MATRIX : array_like, (3, 3)
"""
ICTCP_LMS_P_TO_ICTCP_MATRIX = np.array(
[[2048, 2048, 0],
[6610, -13613, 7003],
[17933, -17390, -543]]) / 4096 # yapf: disable
"""
:math:`LMS_p` *SMPTE ST 2084:2014* encoded normalised cone responses to
:math:`IC_TC_P` colour encoding matrix.
ICTCP_LMS_P_TO_ICTCP_MATRIX : array_like, (3, 3)
"""
ICTCP_ICTCP_TO_LMS_P_MATRIX = np.linalg.inv(ICTCP_LMS_P_TO_ICTCP_MATRIX)
"""
:math:`IC_TC_P` colour encoding to :math:`LMS_p` *SMPTE ST 2084:2014* encoded
normalised cone responses matrix.
ICTCP_ICTCP_TO_LMS_P_MATRIX : array_like, (3, 3)
"""
[docs]def RGB_to_ICTCP(RGB, L_p=10000):
"""
Converts from *Rec. 2020* colourspace to :math:`IC_TC_P` colour encoding.
Parameters
----------
RGB : array_like
*Rec. 2020* colourspace array.
L_p : numeric, optional
Display peak luminance :math:`cd/m^2` for *SMPTE ST 2084:2014*
non-linear encoding.
Returns
-------
ndarray
:math:`IC_TC_P` colour encoding array.
Examples
--------
>>> RGB = np.array([0.35181454, 0.26934757, 0.21288023])
>>> RGB_to_ICTCP(RGB) # doctest: +ELLIPSIS
array([ 0.0955407..., -0.0089063..., 0.0138928...])
"""
LMS = dot_vector(ICTCP_RGB_TO_LMS_MATRIX, RGB)
LMS_p = oetf_ST2084(LMS, L_p)
ICTCP = dot_vector(ICTCP_LMS_P_TO_ICTCP_MATRIX, LMS_p)
return ICTCP
[docs]def ICTCP_to_RGB(ICTCP, L_p=10000):
"""
Converts from :math:`IC_TC_P` colour encoding to *Rec. 2020* colourspace.
Parameters
----------
ICTCP : array_like
:math:`IC_TC_P` colour encoding array.
L_p : numeric, optional
Display peak luminance :math:`cd/m^2` for *SMPTE ST 2084:2014*
non-linear encoding.
Returns
-------
ndarray
*Rec. 2020* colourspace array.
Examples
--------
>>> ICTCP = np.array([0.09554079, -0.00890639, 0.01389286])
>>> ICTCP_to_RGB(ICTCP) # doctest: +ELLIPSIS
array([ 0.3518145..., 0.2693475..., 0.2128802...])
"""
LMS_p = dot_vector(ICTCP_ICTCP_TO_LMS_P_MATRIX, ICTCP)
LMS = eotf_ST2084(LMS_p, L_p)
RGB = dot_vector(ICTCP_LMS_TO_RGB_MATRIX, LMS)
return RGB