"""
:math:`IC_AC_B` Colourspace
===========================
Defines the :math:`IC_AC_B` colourspace transformations:
- :func:`colour.XYZ_to_ICaCb`
- :func:`colour.ICaCb_to_XYZ`
References
----------
- :cite:`Frohlich2017` : Fröhlich, J. (2017). Encoding high dynamic range
and wide color gamut imagery. doi:10.18419/OPUS-9664
"""
from __future__ import annotations
import numpy as np
from colour.hints import ArrayLike, NDArrayFloat
from colour.models import Iab_to_XYZ, XYZ_to_Iab
from colour.models.rgb.transfer_functions import (
eotf_ST2084,
eotf_inverse_ST2084,
)
from colour.utilities import domain_range_scale
__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 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_ICACB_XYZ_TO_LMS",
"MATRIX_ICACB_LMS_TO_XYZ",
"MATRIX_ICACB_XYZ_TO_LMS_2",
"MATRIX_ICACB_LMS_TO_XYZ_2",
"XYZ_to_ICaCb",
"ICaCb_to_XYZ",
]
MATRIX_ICACB_XYZ_TO_LMS: NDArrayFloat = np.array(
[
[0.37613, 0.70431, -0.05675],
[-0.21649, 1.14744, 0.05356],
[0.02567, 0.16713, 0.74235],
]
)
"""*CIE XYZ* tristimulus values to normalised cone responses matrix."""
MATRIX_ICACB_LMS_TO_XYZ: NDArrayFloat = np.linalg.inv(MATRIX_ICACB_XYZ_TO_LMS)
"""Normalised cone responses to *CIE XYZ* tristimulus values matrix."""
MATRIX_ICACB_XYZ_TO_LMS_2: NDArrayFloat = np.array(
[
[0.4949, 0.5037, 0.0015],
[4.2854, -4.5462, 0.2609],
[0.3605, 1.1499, -1.5105],
]
)
"""Normalised non-linear cone responses to :math:`IC_AC_B` colourspace matrix."""
MATRIX_ICACB_LMS_TO_XYZ_2: NDArrayFloat = np.linalg.inv(
MATRIX_ICACB_XYZ_TO_LMS_2
)
""":math:`IC_AC_B` to normalised non-linear cone responses colourspace matrix."""
[docs]def XYZ_to_ICaCb(XYZ: ArrayLike) -> NDArrayFloat:
"""
Convert from *CIE XYZ* tristimulus values to :math:`IC_AC_B` colourspace.
Parameters
----------
XYZ
*CIE XYZ* tristimulus values.
Returns
-------
:class:`numpy.ndarray`
:math:`IC_AC_B` colourspace array.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``XYZ`` | [0, 1] | [0, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``ICaCb`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``Ca`` : [-1, 1] | ``Ca``: [-1, 1] |
| | | |
| | ``Cb`` : [-1, 1] | ``Cb``: [-1, 1] |
+------------+-----------------------+-----------------+
- Input *CIE XYZ* tristimulus values must be adapted to
*CIE Standard Illuminant D Series* *D65*.
References
----------
:cite:`Frohlich2017`
Examples
--------
>>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952])
>>> XYZ_to_ICaCb(XYZ)
array([ 0.06875297, 0.05753352, 0.02081548])
"""
def LMS_to_LMS_p_callable(LMS: ArrayLike) -> NDArrayFloat:
"""
Callable applying the forward non-linearity to the :math:`LMS`
colourspace array.
"""
with domain_range_scale("ignore"):
return eotf_inverse_ST2084(LMS)
return XYZ_to_Iab(
XYZ,
LMS_to_LMS_p_callable,
MATRIX_ICACB_XYZ_TO_LMS,
MATRIX_ICACB_XYZ_TO_LMS_2,
)
[docs]def ICaCb_to_XYZ(ICaCb: ArrayLike) -> NDArrayFloat:
"""
Convert from :math:`IC_AC_B` tristimulus values to *CIE XYZ* colourspace.
Parameters
----------
ICaCb
:math:`IC_AC_B` tristimulus values.
Returns
-------
:class:`numpy.ndarray`
*CIE XYZ* colourspace array.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``ICaCb`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``Ca`` : [-1, 1] | ``Ca``: [-1, 1] |
| | | |
| | ``Cb`` : [-1, 1] | ``Cb``: [-1, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``XYZ`` | [0, 1] | [0, 1] |
+------------+-----------------------+-----------------+
References
----------
:cite:`Frohlich2017`
Examples
--------
>>> XYZ = np.array([0.06875297, 0.05753352, 0.02081548])
>>> ICaCb_to_XYZ(XYZ)
array([ 0.20654008, 0.12197225, 0.05136951])
"""
def LMS_p_to_LMS_callable(LMS_p: ArrayLike) -> NDArrayFloat:
"""
Callable applying the reverse non-linearity to the :math:`LMS_p`
colourspace array.
"""
with domain_range_scale("ignore"):
return eotf_ST2084(LMS_p)
return Iab_to_XYZ(
ICaCb,
LMS_p_to_LMS_callable,
MATRIX_ICACB_LMS_TO_XYZ_2,
MATRIX_ICACB_LMS_TO_XYZ,
)