"""
Fujifilm F-Log Log Encoding
===========================
Defines the *Fujifilm F-Log* log encoding:
- :func:`colour.models.log_encoding_FLog`
- :func:`colour.models.log_decoding_FLog`
References
----------
- :cite:`Fujifilm2016` : Fujifilm. (2016). F-Log Data Sheet Ver.1.0 (pp.
1-4). https://www.fujifilm.com/support/digital_cameras/software/lut/pdf/\
F-Log_DataSheet_E_Ver.1.0.pdf
"""
from __future__ import annotations
import numpy as np
from colour.hints import (
Boolean,
FloatingOrArrayLike,
FloatingOrNDArray,
Integer,
)
from colour.models.rgb.transfer_functions import full_to_legal, legal_to_full
from colour.utilities import Structure, as_float, from_range_1, to_domain_1
__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 Colour Developers"
__license__ = "New BSD License - http://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Production"
__all__ = [
"CONSTANTS_FLOG",
"log_encoding_FLog",
"log_decoding_FLog",
]
CONSTANTS_FLOG: Structure = Structure(
cut1=0.00089,
cut2=0.100537775223865,
a=0.555556,
b=0.009468,
c=0.344676,
d=0.790453,
e=8.735631,
f=0.092864,
)
"""*Fujifilm F-Log* colourspace constants."""
[docs]def log_encoding_FLog(
in_r: FloatingOrArrayLike,
bit_depth: Integer = 10,
out_normalised_code_value: Boolean = True,
in_reflection: Boolean = True,
constants: Structure = CONSTANTS_FLOG,
) -> FloatingOrNDArray:
"""
Define the *Fujifilm F-Log* log encoding curve / opto-electronic transfer
function.
Parameters
----------
in_r
Linear reflection data :math`in`.
bit_depth
Bit depth used for conversion.
out_normalised_code_value
Whether the non-linear *Fujifilm F-Log* data :math:`out` is encoded as
normalised code values.
in_reflection
Whether the light level :math`in` to a camera is reflection.
constants
*Fujifilm F-Log* constants.
Returns
-------
:class:`numpy.floating` or :class:`numpy.ndarray`
Non-linear data :math:`out`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``in_r`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``out_r`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Fujifilm2016`
Examples
--------
>>> log_encoding_FLog(0.18) # doctest: +ELLIPSIS
0.4593184...
The values of *2-2. F-Log Code Value* table in :cite:`Fujifilm2016` are
obtained as follows:
>>> x = np.array([0, 18, 90]) / 100
>>> np.around(log_encoding_FLog(x, 10, False) * 100, 1)
array([ 3.5, 46.3, 73.2])
>>> np.around(log_encoding_FLog(x) * (2 ** 10 - 1)).astype(np.int)
array([ 95, 470, 705])
"""
in_r = to_domain_1(in_r)
if not in_reflection:
in_r = in_r * 0.9
cut1 = constants.cut1
a = constants.a
b = constants.b
c = constants.c
d = constants.d
e = constants.e
f = constants.f
out_r = np.where(
in_r < cut1,
e * in_r + f,
c * np.log10(a * in_r + b) + d,
)
out_r_cv = (
out_r if out_normalised_code_value else legal_to_full(out_r, bit_depth)
)
return as_float(from_range_1(out_r_cv))
[docs]def log_decoding_FLog(
out_r: FloatingOrArrayLike,
bit_depth: Integer = 10,
in_normalised_code_value: Boolean = True,
out_reflection: Boolean = True,
constants: Structure = CONSTANTS_FLOG,
) -> FloatingOrNDArray:
"""
Define the *Fujifilm F-Log* log decoding curve / electro-optical transfer
function.
Parameters
----------
out_r
Non-linear data :math:`out`.
bit_depth
Bit depth used for conversion.
in_normalised_code_value
Whether the non-linear *Fujifilm F-Log* data :math:`out` is encoded as
normalised code values.
out_reflection
Whether the light level :math`in` to a camera is reflection.
constants
*Fujifilm F-Log* constants.
Returns
-------
:class:`numpy.floating` or :class:`numpy.ndarray`
Linear reflection data :math`in`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``out_r`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``in_r`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Fujifilm2016`
Examples
--------
>>> log_decoding_FLog(0.45931845866162124) # doctest: +ELLIPSIS
0.1800000...
"""
out_r = to_domain_1(out_r)
out_r = (
out_r if in_normalised_code_value else full_to_legal(out_r, bit_depth)
)
cut2 = constants.cut2
a = constants.a
b = constants.b
c = constants.c
d = constants.d
e = constants.e
f = constants.f
in_r = np.where(
out_r < cut2,
(out_r - f) / e,
(10 ** ((out_r - d) / c)) / a - b / a,
)
if not out_reflection:
in_r = in_r / 0.9
return as_float(from_range_1(in_r))