"""
Panasonic V-Log Log Encoding
============================
Define the *Panasonic V-Log* log encoding:
- :func:`colour.models.log_encoding_VLog`
- :func:`colour.models.log_decoding_VLog`
References
----------
- :cite:`Panasonic2014a` : Panasonic. (2014). VARICAM V-Log/V-Gamut (pp.
1-7).
http://pro-av.panasonic.net/en/varicam/common/pdf/VARICAM_V-Log_V-Gamut.pdf
"""
from __future__ import annotations
import typing
import numpy as np
if typing.TYPE_CHECKING:
from colour.hints import ArrayLike, NDArrayFloat
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__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Production"
__all__ = [
"CONSTANTS_VLOG",
"log_encoding_VLog",
"log_decoding_VLog",
]
CONSTANTS_VLOG: Structure = Structure(
cut1=0.01, cut2=0.181, b=0.00873, c=0.241514, d=0.598206
)
"""*Panasonic V-Log* constants."""
[docs]
def log_encoding_VLog(
L_in: ArrayLike,
bit_depth: int = 10,
out_normalised_code_value: bool = True,
in_reflection: bool = True,
constants: Structure = CONSTANTS_VLOG,
) -> NDArrayFloat:
"""
Define the *Panasonic V-Log* log encoding curve / opto-electronic transfer
function.
Parameters
----------
L_in
Linear reflection data :math`L_{in}`.
bit_depth
Bit-depth used for conversion.
out_normalised_code_value
Whether the non-linear *Panasonic V-Log* data :math:`V_{out}` is
encoded as normalised code values.
in_reflection
Whether the light level :math`L_{in}` to a camera is reflection.
constants
*Panasonic V-Log* constants.
Returns
-------
:class:`numpy.ndarray`
Non-linear data :math:`V_{out}`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``L_in`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``V_out`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Panasonic2014a`
Examples
--------
>>> log_encoding_VLog(0.18) # doctest: +ELLIPSIS
0.4233114...
The values of *Fig.2.2 V-Log Code Value* table in :cite:`Panasonic2014a`
are obtained as follows:
>>> L_in = np.array([0, 18, 90]) / 100
>>> np.around(log_encoding_VLog(L_in, 10, False) * 100).astype(np.int_)
array([ 7, 42, 61])
>>> np.around(log_encoding_VLog(L_in) * (2**10 - 1)).astype(np.int_)
array([128, 433, 602])
>>> np.around(log_encoding_VLog(L_in) * (2**12 - 1)).astype(np.int_)
array([ 512, 1733, 2409])
Note that some values in the last column values of
*Fig.2.2 V-Log Code Value* table in :cite:`Panasonic2014a` are different
by a code: [512, 1732, 2408].
"""
L_in = to_domain_1(L_in)
if not in_reflection:
L_in = L_in * 0.9
cut1 = constants.cut1
b = constants.b
c = constants.c
d = constants.d
V_out = np.where(
L_in < cut1,
5.6 * L_in + 0.125,
c * np.log10(L_in + b) + d,
)
V_out_cv = V_out if out_normalised_code_value else legal_to_full(V_out, bit_depth)
return as_float(from_range_1(V_out_cv))
[docs]
def log_decoding_VLog(
V_out: ArrayLike,
bit_depth: int = 10,
in_normalised_code_value: bool = True,
out_reflection: bool = True,
constants: Structure = CONSTANTS_VLOG,
) -> NDArrayFloat:
"""
Define the *Panasonic V-Log* log decoding curve / electro-optical transfer
function.
Parameters
----------
V_out
Non-linear data :math:`V_{out}`.
bit_depth
Bit-depth used for conversion.
in_normalised_code_value
Whether the non-linear *Panasonic V-Log* data :math:`V_{out}` is
encoded as normalised code values.
out_reflection
Whether the light level :math`L_{in}` to a camera is reflection.
constants
*Panasonic V-Log* constants.
Returns
-------
:class:`numpy.ndarray`
Linear reflection data :math`L_{in}`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``V_out`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``L_in`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Panasonic2014a`
Examples
--------
>>> log_decoding_VLog(0.423311448760136) # doctest: +ELLIPSIS
0.1799999...
"""
V_out = to_domain_1(V_out)
V_out = V_out if in_normalised_code_value else full_to_legal(V_out, bit_depth)
cut2 = constants.cut2
b = constants.b
c = constants.c
d = constants.d
L_in = np.where(
V_out < cut2,
(V_out - 0.125) / 5.6,
10 ** ((V_out - d) / c) - b,
)
if not out_reflection:
L_in = L_in / 0.9
return as_float(from_range_1(L_in))