#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
sRGB Colourspace
================
Defines the *sRGB* colourspace:
- :attr:`sRGB_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 - 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__ = ['sRGB_PRIMARIES',
'sRGB_ILLUMINANT',
'sRGB_WHITEPOINT',
'sRGB_TO_XYZ_MATRIX',
'XYZ_TO_sRGB_MATRIX',
'sRGB_TRANSFER_FUNCTION',
'sRGB_INVERSE_TRANSFER_FUNCTION',
'sRGB_COLOURSPACE']
sRGB_PRIMARIES = np.array(
[[0.6400, 0.3300],
[0.3000, 0.6000],
[0.1500, 0.0600]])
"""
*sRGB* colourspace primaries.
sRGB_PRIMARIES : ndarray, (3, 2)
"""
sRGB_ILLUMINANT = 'D65'
"""
*sRGB* colourspace whitepoint name as illuminant.
sRGB_WHITEPOINT : unicode
"""
sRGB_WHITEPOINT = ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get(sRGB_ILLUMINANT)
"""
*sRGB* colourspace whitepoint.
sRGB_WHITEPOINT : tuple
"""
sRGB_TO_XYZ_MATRIX = np.array(
[[0.41238656, 0.35759149, 0.18045049],
[0.21263682, 0.71518298, 0.0721802],
[0.01933062, 0.11919716, 0.95037259]])
"""
*sRGB* colourspace to *CIE XYZ* colourspace matrix.
sRGB_TO_XYZ_MATRIX : array_like, (3, 3)
"""
XYZ_TO_sRGB_MATRIX = np.linalg.inv(sRGB_TO_XYZ_MATRIX)
"""
*CIE XYZ* colourspace to *sRGB* colourspace matrix.
XYZ_TO_sRGB_MATRIX : array_like, (3, 3)
"""
def _srgb_transfer_function(value):
"""
Defines the *sRGB* value colourspace transfer function.
Parameters
----------
value : numeric
value.
Returns
-------
numeric
Companded value.
"""
return (value * 12.92
if value <= 0.0031308 else 1.055 * (value ** (1 / 2.4)) - 0.055)
def _srgb_inverse_transfer_function(value):
"""
Defines the *sRGB* value colourspace inverse transfer
function.
Parameters
----------
value : numeric
value.
Returns
-------
numeric
Companded value.
"""
return (value / 12.92
if value <= _srgb_transfer_function(0.0031308) else
((value + 0.055) / 1.055) ** 2.4)
sRGB_TRANSFER_FUNCTION = _srgb_transfer_function
"""
Transfer function from linear to *sRGB* colourspace.
sRGB_TRANSFER_FUNCTION : object
"""
sRGB_INVERSE_TRANSFER_FUNCTION = _srgb_inverse_transfer_function
"""
Inverse transfer function from *sRGB* colourspace to linear.
sRGB_INVERSE_TRANSFER_FUNCTION : object
"""
sRGB_COLOURSPACE = RGB_Colourspace(
'sRGB',
sRGB_PRIMARIES,
sRGB_WHITEPOINT,
sRGB_ILLUMINANT,
sRGB_TO_XYZ_MATRIX,
XYZ_TO_sRGB_MATRIX,
sRGB_TRANSFER_FUNCTION,
sRGB_INVERSE_TRANSFER_FUNCTION)
"""
*sRGB* colourspace.
sRGB_COLOURSPACE : RGB_Colourspace
"""
Colour 0.3