#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Rec. 709 Colourspace
====================
Defines the *Rec. 709* colourspace:
- :attr:`REC_709_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. (2002). Parameter values for
the HDTV standards for production and international programme exchange
BT Series Broadcasting service. In Recommendation ITU-R BT.709-5
(Vol. 5, pp. 1–32). Retrieved from
http://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.709-5-200204-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
__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_709_PRIMARIES',
'REC_709_WHITEPOINT',
'REC_709_ILLUMINANT',
'REC_709_TO_XYZ_MATRIX',
'XYZ_TO_REC_709_MATRIX',
'REC_709_TRANSFER_FUNCTION',
'REC_709_INVERSE_TRANSFER_FUNCTION',
'REC_709_COLOURSPACE']
REC_709_PRIMARIES = np.array(
[[0.6400, 0.3300],
[0.3000, 0.6000],
[0.1500, 0.0600]])
"""
*Rec. 709* colourspace primaries.
REC_709_PRIMARIES : ndarray, (3, 2)
"""
REC_709_ILLUMINANT = 'D65'
"""
*Rec. 709* colourspace whitepoint name as illuminant.
REC_709_ILLUMINANT : unicode
"""
REC_709_WHITEPOINT = ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get(REC_709_ILLUMINANT)
"""
*Rec. 709* colourspace whitepoint.
REC_709_WHITEPOINT : tuple
"""
REC_709_TO_XYZ_MATRIX = np.array(
[[0.41238656, 0.35759149, 0.18045049],
[0.21263682, 0.71518298, 0.0721802],
[0.01933062, 0.11919716, 0.95037259]])
"""
*Rec. 709* colourspace to *CIE XYZ* tristimulus values matrix.
REC_709_TO_XYZ_MATRIX : array_like, (3, 3)
"""
XYZ_TO_REC_709_MATRIX = np.linalg.inv(REC_709_TO_XYZ_MATRIX)
"""
*CIE XYZ* tristimulus values to *Rec. 709* colourspace matrix.
XYZ_TO_REC_709_MATRIX : array_like, (3, 3)
"""
def _rec_709_transfer_function(value):
"""
Defines the *Rec. 709* colourspace transfer function.
Parameters
----------
value : numeric or array_like
Value.
Returns
-------
numeric or ndarray
Companded value.
"""
value = np.asarray(value)
return np.where(value < 0.018,
value * 4.5,
1.099 * (value ** 0.45) - 0.099)
def _rec_709_inverse_transfer_function(value):
"""
Defines the *Rec. 709* colourspace inverse transfer function.
Parameters
----------
value : numeric or array_like
Value.
Returns
-------
numeric or ndarray
Companded value.
"""
value = np.asarray(value)
return np.where(value < _rec_709_transfer_function(0.018),
value / 4.5,
((value + 0.099) / 1.099) ** (1 / 0.45))
REC_709_TRANSFER_FUNCTION = _rec_709_transfer_function
"""
Transfer function from linear to *Rec. 709* colourspace.
REC_709_TRANSFER_FUNCTION : object
"""
REC_709_INVERSE_TRANSFER_FUNCTION = _rec_709_inverse_transfer_function
"""
Inverse transfer function from *Rec. 709* colourspace to linear.
REC_709_INVERSE_TRANSFER_FUNCTION : object
"""
REC_709_COLOURSPACE = RGB_Colourspace(
'Rec. 709',
REC_709_PRIMARIES,
REC_709_WHITEPOINT,
REC_709_ILLUMINANT,
REC_709_TO_XYZ_MATRIX,
XYZ_TO_REC_709_MATRIX,
REC_709_TRANSFER_FUNCTION,
REC_709_INVERSE_TRANSFER_FUNCTION)
"""
*Rec. 709* colourspace.
REC_709_COLOURSPACE : RGB_Colourspace
"""
Colour 0.3