#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Russell RGB Colourspace
=======================
Defines the *Russell RGB* colourspace:
- :attr:`RUSSELL_RGB_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] Cottrell, R. (n.d.). The Russell RGB working color space. Retrieved
from http://www.russellcottrell.com/photo/downloads/RussellRGB.icc
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry.dataset import ILLUMINANTS
from colour.models import normalised_primary_matrix
from colour.models import RGB_Colourspace
__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__ = ['RUSSELL_RGB_PRIMARIES',
'RUSSELL_RGB_ILLUMINANT',
'RUSSELL_RGB_WHITEPOINT',
'RUSSELL_RGB_TO_XYZ_MATRIX',
'XYZ_TO_RUSSELL_RGB_MATRIX',
'RUSSELL_RGB_TRANSFER_FUNCTION',
'RUSSELL_RGB_INVERSE_TRANSFER_FUNCTION',
'RUSSELL_RGB_COLOURSPACE']
RUSSELL_RGB_PRIMARIES = np.array(
[[0.6900, 0.3100],
[0.1800, 0.7700],
[0.1000, 0.0200]])
"""
*Russell RGB* colourspace primaries.
RUSSELL_RGB_PRIMARIES : ndarray, (3, 2)
"""
RUSSELL_RGB_ILLUMINANT = 'D55'
"""
*Russell RGB* colourspace whitepoint name as illuminant.
RUSSELL_RGB_ILLUMINANT : unicode
"""
RUSSELL_RGB_WHITEPOINT = ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get(RUSSELL_RGB_ILLUMINANT)
"""
*Russell RGB* colourspace whitepoint.
RUSSELL_RGB_WHITEPOINT : tuple
"""
RUSSELL_RGB_TO_XYZ_MATRIX = normalised_primary_matrix(
RUSSELL_RGB_PRIMARIES, RUSSELL_RGB_WHITEPOINT)
"""
*Russell RGB* colourspace to *CIE XYZ* colourspace matrix.
RUSSELL_RGB_TO_XYZ_MATRIX : array_like, (3, 3)
"""
XYZ_TO_RUSSELL_RGB_MATRIX = np.linalg.inv(RUSSELL_RGB_TO_XYZ_MATRIX)
"""
*CIE XYZ* colourspace to *Russell RGB* colourspace matrix.
XYZ_TO_RUSSELL_RGB_MATRIX : array_like, (3, 3)
"""
def _russell_rgb_transfer_function(value):
"""
Defines the *Russell RGB* value colourspace transfer function.
Parameters
----------
value : numeric
value.
Returns
-------
numeric
Companded value.
"""
return value ** (1 / 2.2)
def _russell_rgb_inverse_transfer_function(value):
"""
Defines the *Russell RGB* value colourspace inverse transfer
function.
Parameters
----------
value : numeric
value.
Returns
-------
numeric
Companded value.
"""
return value ** 2.2
RUSSELL_RGB_TRANSFER_FUNCTION = _russell_rgb_transfer_function
"""
Transfer function from linear to *Russell RGB* colourspace.
RUSSELL_RGB_TRANSFER_FUNCTION : object
"""
RUSSELL_RGB_INVERSE_TRANSFER_FUNCTION = _russell_rgb_inverse_transfer_function
"""
Inverse transfer function from *Russell RGB* colourspace to linear.
RUSSELL_RGB_INVERSE_TRANSFER_FUNCTION : object
"""
RUSSELL_RGB_COLOURSPACE = RGB_Colourspace(
'Russell RGB',
RUSSELL_RGB_PRIMARIES,
RUSSELL_RGB_WHITEPOINT,
RUSSELL_RGB_ILLUMINANT,
RUSSELL_RGB_TO_XYZ_MATRIX,
XYZ_TO_RUSSELL_RGB_MATRIX,
RUSSELL_RGB_TRANSFER_FUNCTION,
RUSSELL_RGB_INVERSE_TRANSFER_FUNCTION)
"""
*Russell RGB* colourspace.
RUSSELL_RGB_COLOURSPACE : RGB_Colourspace
"""
Colour 0.3