Source code for colour.models.rgb.ycocg

"""
YCoCg Colour Encoding
======================

Defines the *YCoCg* colour encoding related transformations:

-   :func:`colour.RGB_to_YCoCg`
-   :func:`colour.YCoCg_to_RGB`

References
----------
-   :cite:`Malvar2003` : Malvar, H., & Sullivan, G. (2003). YCoCg-R: A Color
    Space with RGB Reversibility and Low Dynamic Range.
    https://www.microsoft.com/en-us/research/wp-content/uploads/2016/06/\
Malvar_Sullivan_YCoCg-R_JVT-I014r3-2.pdf
"""

from __future__ import annotations

import numpy as np

from colour.algebra import vector_dot
from colour.hints import ArrayLike, NDArray

__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__ = "Development"

__all__ = [
    "MATRIX_RGB_TO_YCOCG",
    "MATRIX_YCOCG_TO_RGB",
    "RGB_to_YCoCg",
    "YCoCg_to_RGB",
]

MATRIX_RGB_TO_YCOCG: NDArray = np.array(
    [
        [1 / 4, 1 / 2, 1 / 4],
        [1 / 2, 0, -1 / 2],
        [-1 / 4, 1 / 2, -1 / 4],
    ]
)
"""*R'G'B'* colourspace to *YCoCg* colour encoding matrix."""

MATRIX_YCOCG_TO_RGB: NDArray = np.array(
    [
        [1, 1, -1],
        [1, 0, 1],
        [1, -1, -1],
    ]
)
"""*YCoCg* colour encoding to *R'G'B'* colourspace matrix."""


[docs]def RGB_to_YCoCg(RGB: ArrayLike) -> NDArray: """ Convert an array of *R'G'B'* values to the corresponding *YCoCg* colour encoding values array. Parameters ---------- RGB Input *R'G'B'* array. Returns ------- :class:`numpy.ndarray` *YCoCg* colour encoding array. References ---------- :cite:`Malvar2003` Examples -------- >>> RGB_to_YCoCg(np.array([1.0, 1.0, 1.0])) array([ 1., 0., 0.]) >>> RGB_to_YCoCg(np.array([0.75, 0.5, 0.5])) array([ 0.5625, 0.125 , -0.0625]) """ return vector_dot(MATRIX_RGB_TO_YCOCG, RGB)
[docs]def YCoCg_to_RGB(YCoCg: ArrayLike) -> NDArray: """ Convert an array of *YCoCg* colour encoding values to the corresponding *R'G'B'* values array. Parameters ---------- YCoCg *YCoCg* colour encoding array. Returns ------- :class:`numpy.ndarray` Output *R'G'B'* array. References ---------- :cite:`Malvar2003` Examples -------- >>> YCoCg_to_RGB(np.array([1.0, 0.0, 0.0])) array([ 1., 1., 1.]) >>> YCoCg_to_RGB(np.array([0.5625, 0.125, -0.0625])) array([ 0.75, 0.5 , 0.5 ]) """ return vector_dot(MATRIX_YCOCG_TO_RGB, YCoCg)