#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Rec. 2020 Colourspace
=====================
Defines the *Rec. 2020* colourspace:
- :attr:`REC_2020_COLOURSPACE`.
See Also
--------
`RGB Colourspaces IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/models/rgb.ipynb>`_ # noqa
References
----------
.. [1] International Telecommunication Union. (2014). Parameter values for
ultra-high definition television systems for production and
international programme exchange. In Recommendation ITU-R BT.2020
(Vol. 1, pp. 1–8). Retrieved from
http://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.2020-1-201406-I!!PDF-E.pdf # noqa
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry import ILLUMINANTS
from colour.models import RGB_Colourspace, normalised_primary_matrix
from colour.utilities import Structure
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013 - 2014 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = ['REC_2020_PRIMARIES',
'REC_2020_ILLUMINANT',
'REC_2020_WHITEPOINT',
'REC_2020_TO_XYZ_MATRIX',
'XYZ_TO_REC_2020_MATRIX',
'REC_2020_CONSTANTS',
'REC_2020_TRANSFER_FUNCTION',
'REC_2020_INVERSE_TRANSFER_FUNCTION',
'REC_2020_COLOURSPACE']
REC_2020_PRIMARIES = np.array(
[[0.708, 0.292],
[0.170, 0.797],
[0.131, 0.046]])
"""
*Rec. 2020* colourspace primaries.
REC_2020_PRIMARIES : ndarray, (3, 2)
"""
REC_2020_ILLUMINANT = 'D65'
"""
*Rec. 2020* colourspace whitepoint name as illuminant.
REC_2020_ILLUMINANT : unicode
"""
REC_2020_WHITEPOINT = ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get(REC_2020_ILLUMINANT)
"""
*Rec. 2020* colourspace whitepoint.
REC_2020_WHITEPOINT : tuple
"""
REC_2020_TO_XYZ_MATRIX = normalised_primary_matrix(REC_2020_PRIMARIES,
REC_2020_WHITEPOINT)
"""
*Rec. 2020* colourspace to *CIE XYZ* colourspace matrix.
REC_2020_TO_XYZ_MATRIX : array_like, (3, 3)
"""
XYZ_TO_REC_2020_MATRIX = np.linalg.inv(REC_2020_TO_XYZ_MATRIX)
"""
*CIE XYZ* colourspace to *Rec. 2020* colourspace matrix.
XYZ_TO_REC_2020_MATRIX : array_like, (3, 3)
"""
REC_2020_CONSTANTS = Structure(alpha=lambda x: 1.099 if x else 1.0993,
beta=lambda x: 0.018 if x else 0.0181)
"""
*CIE XYZ* constants.
REC_2020_CONSTANTS : Structure
"""
def _rec_2020_transfer_function(value, is_10_bits_system=True):
"""
Defines the *Rec. 2020* colourspace transfer function.
Parameters
----------
value : numeric
value.
is_10_bits_system : bool
*Rec. 709* *alpha* and *beta* constants are used if system is 10 bit.
Returns
-------
numeric
Companded value.
"""
a = REC_2020_CONSTANTS.alpha(is_10_bits_system)
b = REC_2020_CONSTANTS.beta(is_10_bits_system)
return (value * 4.5
if value < b else
a * (value ** 0.45) - (a - 1))
def _rec_2020_inverse_transfer_function(value, is_10_bits_system=True):
"""
Defines the *Rec. 2020* colourspace inverse transfer function.
Parameters
----------
value : numeric
value.
is_10_bits_system : bool
*Rec. 709* *alpha* and *beta* constants are used if system is 10 bit.
Returns
-------
numeric
Companded value.
"""
a = REC_2020_CONSTANTS.alpha(is_10_bits_system)
b = REC_2020_CONSTANTS.beta(is_10_bits_system)
return (value / 4.5
if value < _rec_2020_transfer_function(b) else
((value + (a - 1)) / a) ** (1 / 0.45))
REC_2020_TRANSFER_FUNCTION = _rec_2020_transfer_function
"""
Transfer function from linear to *Rec. 2020* colourspace.
REC_2020_TRANSFER_FUNCTION : object
"""
REC_2020_INVERSE_TRANSFER_FUNCTION = _rec_2020_inverse_transfer_function
"""
Inverse transfer function from *Rec. 2020* colourspace to linear.
REC_2020_INVERSE_TRANSFER_FUNCTION : object
"""
REC_2020_COLOURSPACE = RGB_Colourspace(
'Rec. 2020',
REC_2020_PRIMARIES,
REC_2020_WHITEPOINT,
REC_2020_ILLUMINANT,
REC_2020_TO_XYZ_MATRIX,
XYZ_TO_REC_2020_MATRIX,
REC_2020_TRANSFER_FUNCTION,
REC_2020_INVERSE_TRANSFER_FUNCTION)
"""
*Rec. 2020* colourspace.
REC_2020_COLOURSPACE : RGB_Colourspace
"""
Colour 0.3