"""
Ragoo and Farup (2021) Optimised IPT Colourspace
================================================
Define the *Ragoo and Farup (2021)* *Optimised IPT* colourspace
transformations:
- :func:`colour.XYZ_to_IPT_Ragoo2021`
- :func:`colour.IPT_Ragoo2021_to_XYZ`
References
----------
- :cite:`Ragoo2021` : Ragoo, L., & Farup, I. (2021). Optimising a Euclidean
Colour Space Transform for Colour Order and Perceptual Uniformity.
Color and Imaging Conference, 29(1), 282-287.
doi:10.2352/issn.2169-2629.2021.29.282
"""
from __future__ import annotations
import typing
from functools import partial
import numpy as np
from colour.algebra import spow
if typing.TYPE_CHECKING:
from colour.hints import ArrayLike, NDArrayFloat
from colour.models import Iab_to_XYZ, XYZ_to_Iab
__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 Colour Developers"
__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Production"
__all__ = [
"MATRIX_IPT_XYZ_TO_LMS",
"MATRIX_IPT_LMS_TO_XYZ",
"MATRIX_IPT_LMS_P_TO_IPT",
"MATRIX_IPT_IPT_TO_LMS_P",
"XYZ_to_IPT_Ragoo2021",
"IPT_Ragoo2021_to_XYZ",
]
MATRIX_IPT_XYZ_TO_LMS: NDArrayFloat = np.array(
[
[0.4321, 0.6906, -0.0930],
[-0.1793, 1.1458, 0.0226],
[0.0631, 0.1532, 0.7226],
]
)
"""*CIE XYZ* tristimulus values to normalised cone responses matrix."""
MATRIX_IPT_LMS_TO_XYZ: NDArrayFloat = np.linalg.inv(MATRIX_IPT_XYZ_TO_LMS)
"""Normalised cone responses to *CIE XYZ* tristimulus values matrix."""
MATRIX_IPT_LMS_P_TO_IPT: NDArrayFloat = np.array(
[
[0.3037, 0.6688, 0.0276],
[3.9247, -4.7339, 0.8093],
[1.5932, -0.5205, -1.0727],
]
)
"""
Normalised non-linear cone responses to *Ragoo and Farup (2021)*
*Optimised IPT* colourspace matrix.
"""
MATRIX_IPT_IPT_TO_LMS_P: NDArrayFloat = np.linalg.inv(MATRIX_IPT_LMS_P_TO_IPT)
"""
*Ragoo and Farup (2021)* *Optimised IPT* colourspace to normalised
non-linear cone responses matrix.
"""
[docs]
def XYZ_to_IPT_Ragoo2021(XYZ: ArrayLike) -> NDArrayFloat:
"""
Convert from *CIE XYZ* tristimulus values to
*Ragoo and Farup (2021)* *Optimised IPT* colourspace.
Parameters
----------
XYZ
*CIE XYZ* tristimulus values.
Returns
-------
:class:`numpy.ndarray`
*Ragoo and Farup (2021)* *Optimised IPT* colourspace array.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``XYZ`` | [0, 1] | [0, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``IPT`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``P`` : [-1, 1] | ``P`` : [-1, 1] |
| | | |
| | ``T`` : [-1, 1] | ``T`` : [-1, 1] |
+------------+-----------------------+-----------------+
- Input *CIE XYZ* tristimulus values must be adapted to
*CIE Standard Illuminant D Series* *D65*.
References
----------
:cite:`Ragoo2021`
Examples
--------
>>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952])
>>> XYZ_to_IPT_Ragoo2021(XYZ) # doctest: +ELLIPSIS
array([ 0.4224824..., 0.2910514..., 0.2041066...])
"""
return XYZ_to_Iab(
XYZ,
partial(spow, p=0.4071),
MATRIX_IPT_XYZ_TO_LMS,
MATRIX_IPT_LMS_P_TO_IPT,
)
[docs]
def IPT_Ragoo2021_to_XYZ(IPT: ArrayLike) -> NDArrayFloat:
"""
Convert from *Ragoo and Farup (2021)* *Optimised IPT* colourspace to
*CIE XYZ* tristimulus values.
Parameters
----------
IPT
*Ragoo and Farup (2021)* *Optimised IPT* colourspace array.
Returns
-------
:class:`numpy.ndarray`
*CIE XYZ* tristimulus values.
Notes
-----
+------------+-----------------------+-----------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``IPT`` | ``I`` : [0, 1] | ``I`` : [0, 1] |
| | | |
| | ``P`` : [-1, 1] | ``P`` : [-1, 1] |
| | | |
| | ``T`` : [-1, 1] | ``T`` : [-1, 1] |
+------------+-----------------------+-----------------+
+------------+-----------------------+-----------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+=================+
| ``XYZ`` | [0, 1] | [0, 1] |
+------------+-----------------------+-----------------+
References
----------
:cite:`Ragoo2021`
Examples
--------
>>> IPT = np.array([0.42248243, 0.2910514, 0.20410663])
>>> IPT_Ragoo2021_to_XYZ(IPT) # doctest: +ELLIPSIS
array([ 0.2065400..., 0.1219722..., 0.0513695...])
"""
return Iab_to_XYZ(
IPT,
partial(spow, p=1 / 0.4071),
MATRIX_IPT_IPT_TO_LMS_P,
MATRIX_IPT_LMS_TO_XYZ,
)
