Source code for colour.models.rgb.transfer_functions.oppo_o_log
"""
OPPO O-Log Profile Log Encoding
===============================
Define the *OPPO O-Log Profile* log encoding.
- :func:`colour.models.log_encoding_OPPOOLog`
- :func:`colour.models.log_decoding_OPPOOLog`
References
----------
- :cite:`Lai2025` : Lai, Z., Qu, T., Yan, C., & Chow, Z. (2025). OPPO O-Log \
- Whitepaper. Retrieved March 17, 2026, from https://www.oppo.com/content/\
dam/oppo_com/en/mkt/footer/OPPO_O-Log_Profile_WhitePaper_V1.pdf
"""
from __future__ import annotations
import numpy as np
from colour.hints import ( # noqa: TC001
Domain1,
Range1,
)
from colour.utilities import Structure, as_float, from_range_1, optional, 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__ = [
"CONSTANTS_OPPO_O_LOG",
"log_encoding_OPPOOLog",
"log_decoding_OPPOOLog",
]
CONSTANTS_OPPO_O_LOG: Structure = Structure(
gamma=0.139,
beta=0.019,
delta=0.614,
)
"""*OPPO O-Log Profile* constants."""
[docs]
def log_encoding_OPPOOLog(
R: Domain1,
constants: Structure | None = None,
) -> Range1:
"""
Apply the *OPPO O-Log Profile* log encoding opto-electronic transfer
function (OETF).
Parameters
----------
R
Linear reflection data :math:`R`.
constants
*OPPO O-Log Profile* constants.
Returns
-------
:class:`numpy.ndarray`
Logarithmically encoded value :math:`P`.
References
----------
:cite:`Lai2025`
Notes
-----
- The scene reflection signal :math:`R` captured by the camera is
represented using a floating point encoding. The :math:`R` value
of 0.18 corresponds to the signal produced by an 18% reflectance
reference gray chart.
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``R`` | 1 | 1 |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``P`` | 1 | 1 |
+------------+-----------------------+---------------+
Examples
--------
>>> log_encoding_OPPOOLog(0.18) # doctest: +ELLIPSIS
np.float64(0.3895913...)
"""
R = to_domain_1(R)
constants = optional(constants, CONSTANTS_OPPO_O_LOG)
gamma = constants.gamma
beta = constants.beta
delta = constants.delta
P = gamma * np.log(R + beta) + delta
return as_float(from_range_1(P))
[docs]
def log_decoding_OPPOOLog(
P: Domain1,
constants: Structure | None = None,
) -> Range1:
"""
Apply the *OPPO O-Log Profile* log decoding inverse opto-electronic
transfer function (OETF).
Parameters
----------
P
Logarithmically encoded value :math:`P`.
constants
*OPPO O-Log Profile* constants.
Returns
-------
:class:`numpy.ndarray`
Linear reflection data :math:`R`.
References
----------
:cite:`Lai2025`
Notes
-----
- The captured pixel :math:`P` value uses floating point encoding
normalized to the [0, 1] range.
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``P`` | 1 | 1 |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``R`` | 1 | 1 |
+------------+-----------------------+---------------+
Examples
--------
>>> log_decoding_OPPOOLog(0.38959139) # doctest: +ELLIPSIS
np.float64(0.1800000...)
"""
P = to_domain_1(P)
constants = optional(constants, CONSTANTS_OPPO_O_LOG)
gamma = constants.gamma
beta = constants.beta
delta = constants.delta
R = np.exp((P - delta) / gamma) - beta
return as_float(from_range_1(R))
