# -*- coding: utf-8 -*-
"""
:math:`IC_TC_P` Colour Encoding
===============================
Defines the :math:`IC_TC_P` colour encoding related transformations:
- :func:`colour.RGB_to_ICTCP`
- :func:`colour.ICTCP_to_RGB`
References
----------
- :cite:`Dolby2016a` : Dolby. (2016). WHAT IS ICTCP? - INTRODUCTION.
https://www.dolby.com/us/en/technologies/dolby-vision/ICtCp-white-paper.pdf
- :cite:`Lu2016c` : Lu, T., Pu, F., Yin, P., Chen, T., Husak, W., Pytlarz,
J., Atkins, R., Froehlich, J., & Su, G.-M. (2016). ITP Colour Space and Its
Compression Performance for High Dynamic Range and Wide Colour Gamut Video
Distribution. ZTE Communications, 14(1), 32-38.
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.models.rgb.transfer_functions import (eotf_inverse_ST2084,
eotf_ST2084)
from colour.utilities import (domain_range_scale, vector_dot, from_range_1,
to_domain_1)
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - 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__ = [
'MATRIX_ICTCP_RGB_TO_LMS', 'MATRIX_ICTCP_LMS_TO_RGB',
'MATRIX_ICTCP_LMS_P_TO_ICTCP', 'MATRIX_ICTCP_ICTCP_TO_LMS_P',
'RGB_to_ICTCP', 'ICTCP_to_RGB'
]
MATRIX_ICTCP_RGB_TO_LMS = np.array([
[1688, 2146, 262],
[683, 2951, 462],
[99, 309, 3688],
]) / 4096
"""
*ITU-R BT.2020* colourspace to normalised cone responses matrix.
MATRIX_ICTCP_RGB_TO_LMS : array_like, (3, 3)
"""
MATRIX_ICTCP_LMS_TO_RGB = np.linalg.inv(MATRIX_ICTCP_RGB_TO_LMS)
"""
:math:`IC_TC_P` colourspace normalised cone responses to *ITU-R BT.2020*
colourspace matrix.
MATRIX_ICTCP_LMS_TO_RGB : array_like, (3, 3)
"""
MATRIX_ICTCP_LMS_P_TO_ICTCP = np.array([
[2048, 2048, 0],
[6610, -13613, 7003],
[17933, -17390, -543],
]) / 4096
"""
:math:`LMS_p` *SMPTE ST 2084:2014* encoded normalised cone responses to
:math:`IC_TC_P` colour encoding matrix.
MATRIX_ICTCP_LMS_P_TO_ICTCP : array_like, (3, 3)
"""
MATRIX_ICTCP_ICTCP_TO_LMS_P = np.linalg.inv(MATRIX_ICTCP_LMS_P_TO_ICTCP)
"""
:math:`IC_TC_P` colour encoding to :math:`LMS_p` *SMPTE ST 2084:2014* encoded
normalised cone responses matrix.
MATRIX_ICTCP_ICTCP_TO_LMS_P : array_like, (3, 3)
"""
[docs]def RGB_to_ICTCP(RGB, L_p=10000):
"""
Converts from *ITU-R BT.2020* colourspace to :math:`IC_TC_P` colour
encoding.
Parameters
----------
RGB : array_like
*ITU-R BT.2020* colourspace array.
L_p : numeric, optional
Display peak luminance :math:`cd/m^2` for *SMPTE ST 2084:2014*
non-linear encoding. This parameter should stay at its default
:math:`10000 cd/m^2` value for practical applications. It is exposed so
that the definition can be used as a fitting function.
Returns
-------
ndarray
:math:`IC_TC_P` colour encoding array.
Warnings
--------
The underlying *SMPTE ST 2084:2014* transfer function is an absolute
transfer function.
Notes
-----
- The underlying *SMPTE ST 2084:2014* transfer function is an absolute
transfer function, thus the domain and range values for the *Reference*
and *1* scales are only indicative that the data is not affected by
scale transformations. The effective domain of *SMPTE ST 2084:2014*
inverse electro-optical transfer function (EOTF / EOCF) is
[0.0001, 10000].
+------------+-----------------------+------------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+==================+
| ``RGB`` | ``UN`` | ``UN`` |
+------------+-----------------------+------------------+
+------------+-----------------------+------------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+==================+
| ``ICTCP`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``CT`` : [-1, 1] | ``CT`` : [-1, 1] |
| | | |
| | ``CP`` : [-1, 1] | ``CP`` : [-1, 1] |
+------------+-----------------------+------------------+
References
----------
:cite:`Dolby2016a`, :cite:`Lu2016c`
Examples
--------
>>> RGB = np.array([0.45620519, 0.03081071, 0.04091952])
>>> RGB_to_ICTCP(RGB) # doctest: +ELLIPSIS
array([ 0.0735136..., 0.0047525..., 0.0935159...])
"""
RGB = to_domain_1(RGB)
LMS = vector_dot(MATRIX_ICTCP_RGB_TO_LMS, RGB)
with domain_range_scale('ignore'):
LMS_p = eotf_inverse_ST2084(LMS, L_p)
ICTCP = vector_dot(MATRIX_ICTCP_LMS_P_TO_ICTCP, LMS_p)
return from_range_1(ICTCP)
[docs]def ICTCP_to_RGB(ICTCP, L_p=10000):
"""
Converts from :math:`IC_TC_P` colour encoding to *ITU-R BT.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. This parameter should stay at its default
:math:`10000 cd/m^2` value for practical applications. It is exposed so
that the definition can be used as a fitting function.
Returns
-------
ndarray
*ITU-R BT.2020* colourspace array.
Warnings
--------
The underlying *SMPTE ST 2084:2014* transfer function is an absolute
transfer function.
Notes
-----
- The underlying *SMPTE ST 2084:2014* transfer function is an absolute
transfer function, thus the domain and range values for the *Reference*
and *1* scales are only indicative that the data is not affected by
scale transformations.
+------------+-----------------------+------------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+==================+
| ``ICTCP`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``CT`` : [-1, 1] | ``CT`` : [-1, 1] |
| | | |
| | ``CP`` : [-1, 1] | ``CP`` : [-1, 1] |
+------------+-----------------------+------------------+
+------------+-----------------------+------------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+==================+
| ``RGB`` | ``UN`` | ``UN`` |
+------------+-----------------------+------------------+
References
----------
:cite:`Dolby2016a`, :cite:`Lu2016c`
Examples
--------
>>> ICTCP = np.array([0.07351364, 0.00475253, 0.09351596])
>>> ICTCP_to_RGB(ICTCP) # doctest: +ELLIPSIS
array([ 0.4562052..., 0.0308107..., 0.0409195...])
"""
ICTCP = to_domain_1(ICTCP)
LMS_p = vector_dot(MATRIX_ICTCP_ICTCP_TO_LMS_P, ICTCP)
with domain_range_scale('ignore'):
LMS = eotf_ST2084(LMS_p, L_p)
RGB = vector_dot(MATRIX_ICTCP_LMS_TO_RGB, LMS)
return from_range_1(RGB)