Source code for colour.models.dataset.rec_2020

#!/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 - 2015 - 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* tristimulus values 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* tristimulus values 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)
"""
*Rec. 2020* colourspace 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 or array_like
        Value.
    is_10_bits_system : bool
        *Rec. 709* *alpha* and *beta* constants are used if system is 10 bit.

    Returns
    -------
    numeric or ndarray
        Companded value.
    """

    value = np.asarray(value)

    a = REC_2020_CONSTANTS.alpha(is_10_bits_system)
    b = REC_2020_CONSTANTS.beta(is_10_bits_system)
    return np.where(value < b,
                    value * 4.5,
                    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 or array_like
        Value.
    is_10_bits_system : bool
        *Rec. 709* *alpha* and *beta* constants are used if system is 10 bit.

    Returns
    -------
    numeric or ndarray
        Companded value.
    """

    value = np.asarray(value)

    a = REC_2020_CONSTANTS.alpha(is_10_bits_system)
    b = REC_2020_CONSTANTS.beta(is_10_bits_system)
    return np.where(value < _rec_2020_transfer_function(b),
                    value / 4.5,
                    ((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
"""