Source code for colour.models.rgb.transfer_functions.panasonic_vlog

# -*- coding: utf-8 -*-
"""
Panasonic V-Log Log Encoding
============================

Defines the *Panasonic V-Log* log encoding:

-   :func:`colour.models.log_encoding_VLog`
-   :func:`colour.models.log_decoding_VLog`

See Also
--------
`RGB Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/rgb.ipynb>`_

References
----------
-   :cite:`Panasonic2014a` : Panasonic. (2014). VARICAM V-Log/V-Gamut.
    Retrieved from http://pro-av.panasonic.net/en/varicam/common/pdf/\
VARICAM_V-Log_V-Gamut.pdf
"""

from __future__ import division, unicode_literals

import numpy as np

from colour.models.rgb.transfer_functions import full_to_legal, legal_to_full
from colour.utilities import Structure, as_numeric

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2018 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'

__all__ = ['VLOG_CONSTANTS', 'log_encoding_VLog', 'log_decoding_VLog']

VLOG_CONSTANTS = Structure(
    cut1=0.01, cut2=0.181, b=0.00873, c=0.241514, d=0.598206)
"""
*Panasonic V-Log* colourspace constants.

VLOG_CONSTANTS : Structure
"""


[docs]def log_encoding_VLog(L_in, bit_depth=10, out_legal=True, in_reflection=True): """ Defines the *Panasonic V-Log* log encoding curve / opto-electronic transfer function. Parameters ---------- L_in : numeric or array_like Linear reflection data :math`L_{in}`. bit_depth : int, optional Bit depth used for conversion. out_legal : bool, optional Whether the non-linear *Panasonic V-Log* data :math:`V_{out}` is encoded in legal range. in_reflection : bool, optional Whether the light level :math`L_{in}` to a camera is reflection. Returns ------- numeric or ndarray Non-linear data :math:`V_{out}`. References ---------- - :cite:`Panasonic2014a` Examples -------- >>> log_encoding_VLog(0.18) # doctest: +ELLIPSIS 0.4233114... """ L_in = np.asarray(L_in) if not in_reflection: L_in = L_in * 0.9 cut1 = VLOG_CONSTANTS.cut1 b = VLOG_CONSTANTS.b c = VLOG_CONSTANTS.c d = VLOG_CONSTANTS.d V_out = np.where(L_in < cut1, 5.6 * L_in + 0.125, c * np.log10(L_in + b) + d) V_out = V_out if out_legal else legal_to_full(V_out, bit_depth) return as_numeric(V_out)
[docs]def log_decoding_VLog(V_out, bit_depth=10, in_legal=True, out_reflection=True): """ Defines the *Panasonic V-Log* log decoding curve / electro-optical transfer function. Parameters ---------- V_out : numeric or array_like Non-linear data :math:`V_{out}`. bit_depth : int, optional Bit depth used for conversion. in_legal : bool, optional Whether the non-linear *Panasonic V-Log* data :math:`V_{out}` is encoded in legal range. out_reflection : bool, optional Whether the light level :math`L_{in}` to a camera is reflection. Returns ------- numeric or ndarray Linear reflection data :math`L_{in}`. References ---------- - :cite:`Panasonic2014a` Examples -------- >>> log_decoding_VLog(0.423311448760136) # doctest: +ELLIPSIS 0.1799999... """ V_out = np.asarray(V_out) V_out = V_out if in_legal else full_to_legal(V_out, bit_depth) cut2 = VLOG_CONSTANTS.cut2 b = VLOG_CONSTANTS.b c = VLOG_CONSTANTS.c d = VLOG_CONSTANTS.d L_in = np.where(V_out < cut2, (V_out - 0.125) / 5.6, np.power(10, ((V_out - d) / c)) - b) if not out_reflection: L_in = L_in / 0.9 return as_numeric(L_in)