Source code for colour.models.rgb.ycocg
"""
YCoCg Colour Encoding
======================
Define 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 typing
import numpy as np
from colour.algebra import vecmul
if typing.TYPE_CHECKING:
from colour.hints import ArrayLike, NDArrayFloat
__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__ = "Development"
__all__ = [
"MATRIX_RGB_TO_YCOCG",
"MATRIX_YCOCG_TO_RGB",
"RGB_to_YCoCg",
"YCoCg_to_RGB",
]
MATRIX_RGB_TO_YCOCG: NDArrayFloat = 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: NDArrayFloat = 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) -> NDArrayFloat:
"""
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 vecmul(MATRIX_RGB_TO_YCOCG, RGB)
[docs]
def YCoCg_to_RGB(YCoCg: ArrayLike) -> NDArrayFloat:
"""
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 vecmul(MATRIX_YCOCG_TO_RGB, YCoCg)
