Source code for colour.models.oklab

"""
Oklab Colourspace
=================

Defines the *Oklab* colourspace transformations:

-   :func:`colour.XYZ_to_Oklab`
-   :func:`colour.Oklab_to_XYZ`

References
----------
-   :cite:`Ottosson2020` : Ottosson, B. (2020). A perceptual color space for
    image processing. Retrieved December 24, 2020, from
    https://bottosson.github.io/posts/oklab/
"""

from __future__ import annotations

import numpy as np
from functools import partial

from colour.algebra import spow
from colour.models import Iab_to_XYZ, XYZ_to_Iab
from colour.hints import ArrayLike, NDArrayFloat

__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_1_XYZ_TO_LMS",
    "MATRIX_1_LMS_TO_XYZ",
    "MATRIX_2_LMS_TO_LAB",
    "MATRIX_2_LAB_TO_LMS",
    "XYZ_to_Oklab",
    "Oklab_to_XYZ",
]

MATRIX_1_XYZ_TO_LMS: NDArrayFloat = np.array(
    [
        [0.8189330101, 0.3618667424, -0.1288597137],
        [0.0329845436, 0.9293118715, 0.0361456387],
        [0.0482003018, 0.2643662691, 0.6338517070],
    ]
)
"""*CIE XYZ* tristimulus values to normalised cone responses matrix."""

MATRIX_1_LMS_TO_XYZ: NDArrayFloat = np.linalg.inv(MATRIX_1_XYZ_TO_LMS)
"""Normalised cone responses to *CIE XYZ* tristimulus values matrix."""

MATRIX_2_LMS_TO_LAB: NDArrayFloat = np.array(
    [
        [0.2104542553, 0.7936177850, -0.0040720468],
        [1.9779984951, -2.4285922050, 0.4505937099],
        [0.0259040371, 0.7827717662, -0.8086757660],
    ]
)
"""Normalised cone responses to *Oklab* colourspace matrix."""

MATRIX_2_LAB_TO_LMS: NDArrayFloat = np.linalg.inv(MATRIX_2_LMS_TO_LAB)
"""*Oklab* colourspace to normalised cone responses matrix."""


[docs]def XYZ_to_Oklab(XYZ: ArrayLike) -> NDArrayFloat: """ Convert from *CIE XYZ* tristimulus values to *Oklab* colourspace. Parameters ---------- XYZ *CIE XYZ* tristimulus values. Returns ------- :class:`numpy.ndarray` *Oklab* colourspace array. Notes ----- +------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +------------+-----------------------+-----------------+ +------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+=================+ | ``Lab`` | ``L`` : [0, 1] | ``L`` : [0, 1] | | | | | | | ``a`` : [-1, 1] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-1, 1] | ``b`` : [-1, 1] | +------------+-----------------------+-----------------+ - Input *CIE XYZ* tristimulus values must be adapted to *CIE Standard Illuminant D Series* *D65*. References ---------- :cite:`Ottosson2020` Examples -------- >>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952]) >>> XYZ_to_Oklab(XYZ) # doctest: +ELLIPSIS array([ 0.5163401..., 0.154695 ..., 0.0628957...]) """ return XYZ_to_Iab( XYZ, partial(spow, p=1 / 3), MATRIX_1_XYZ_TO_LMS, MATRIX_2_LMS_TO_LAB, )
[docs]def Oklab_to_XYZ(Lab: ArrayLike) -> NDArrayFloat: """ Convert from *Oklab* colourspace to *CIE XYZ* tristimulus values. Parameters ---------- Lab *Oklab* colourspace array. Returns ------- :class:`numpy.ndarray` *CIE XYZ* tristimulus values. Notes ----- +------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+=================+ | ``Lab`` | ``L`` : [0, 1] | ``L`` : [0, 1] | | | | | | | ``a`` : [-1, 1] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-1, 1] | ``b`` : [-1, 1] | +------------+-----------------------+-----------------+ +------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +------------+-----------------------+-----------------+ References ---------- :cite:`Ottosson2020` Examples -------- >>> Lab = np.array([0.51634019, 0.15469500, 0.06289579]) >>> Oklab_to_XYZ(Lab) # doctest: +ELLIPSIS array([ 0.2065400..., 0.1219722..., 0.0513695...]) """ return Iab_to_XYZ( Lab, partial(spow, p=3), MATRIX_2_LAB_TO_LMS, MATRIX_1_LMS_TO_XYZ, )