Source code for colour.models.rgb.ictcp

# -*- 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, dot_vector, 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__ = [
    '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
"""
*ITU-R BT.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 *ITU-R BT.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
"""
: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 *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. Returns ------- ndarray :math:`IC_TC_P` colour encoding array. Notes ----- +------------+-----------------------+------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+==================+ | ``RGB`` | [0, 1] | [0, 1] | +------------+-----------------------+------------------+ +------------+-----------------------+------------------+ | **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 = dot_vector(ICTCP_RGB_TO_LMS_MATRIX, RGB) with domain_range_scale('ignore'): LMS_p = eotf_inverse_ST2084(LMS, L_p) ICTCP = dot_vector(ICTCP_LMS_P_TO_ICTCP_MATRIX, 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. Returns ------- ndarray *ITU-R BT.2020* colourspace array. Notes ----- +------------+-----------------------+------------------+ | **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`` | [0, 1] | [0, 1] | +------------+-----------------------+------------------+ 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 = dot_vector(ICTCP_ICTCP_TO_LMS_P_MATRIX, ICTCP) with domain_range_scale('ignore'): LMS = eotf_ST2084(LMS_p, L_p) RGB = dot_vector(ICTCP_LMS_TO_RGB_MATRIX, LMS) return from_range_1(RGB)