Source code for colour.models.rgb.transfer_functions.srgb
"""
SRGB
====
Define the *sRGB* electro-optical transfer function (EOTF) and its
inverse:
- :func:`colour.models.eotf_inverse_sRGB`
- :func:`colour.models.eotf_sRGB`
References
----------
- :cite:`InternationalElectrotechnicalCommission1999a` : International
Electrotechnical Commission. (1999). IEC 61966-2-1:1999 - Multimedia
systems and equipment - Colour measurement and management - Part 2-1:
Colour management - Default RGB colour space - sRGB (p. 51).
https://webstore.iec.ch/publication/6169
- :cite:`InternationalTelecommunicationUnion2015i` : International
Telecommunication Union. (2015). Recommendation ITU-R BT.709-6 - Parameter
values for the HDTV standards for production and international programme
exchange BT Series Broadcasting service (pp. 1-32).
https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.709-6-201506-I!!PDF-E.pdf
"""
from __future__ import annotations
import numpy as np
from colour.algebra import spow
from colour.hints import ArrayLike, NDArrayFloat
from colour.utilities import (
as_float,
domain_range_scale,
from_range_1,
to_domain_1,
)
__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__ = [
"eotf_inverse_sRGB",
"eotf_sRGB",
]
[docs]
def eotf_inverse_sRGB(L: ArrayLike) -> NDArrayFloat:
"""
Define the *IEC 61966-2-1:1999* *sRGB* inverse electro-optical transfer
function (EOTF).
Parameters
----------
L
*Luminance* :math:`L` of the image.
Returns
-------
:class:`numpy.ndarray`
Corresponding electrical signal :math:`V`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``L`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``V`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`InternationalElectrotechnicalCommission1999a`,
:cite:`InternationalTelecommunicationUnion2015i`
Examples
--------
>>> eotf_inverse_sRGB(0.18) # doctest: +ELLIPSIS
0.4613561...
"""
L = to_domain_1(L)
V = np.where(L <= 0.0031308, L * 12.92, 1.055 * spow(L, 1 / 2.4) - 0.055)
return as_float(from_range_1(V))
[docs]
def eotf_sRGB(V: ArrayLike) -> NDArrayFloat:
"""
Define the *IEC 61966-2-1:1999* *sRGB* electro-optical transfer function
(EOTF).
Parameters
----------
V
Electrical signal :math:`V`.
Returns
-------
:class:`numpy.ndarray`
Corresponding *luminance* :math:`L` of the image.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``V`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``L`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`InternationalElectrotechnicalCommission1999a`,
:cite:`InternationalTelecommunicationUnion2015i`
Examples
--------
>>> eotf_sRGB(0.461356129500442) # doctest: +ELLIPSIS
0.1...
"""
V = to_domain_1(V)
with domain_range_scale("ignore"):
L = np.where(
eotf_inverse_sRGB(0.0031308) >= V,
V / 12.92,
spow((V + 0.055) / 1.055, 2.4),
)
return as_float(from_range_1(L))
