#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Colour Rendering Index
======================
Defines *colour rendering index* computation objects:
- :func:`colour_rendering_index`
See Also
--------
`Colour Rendering Index IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/quality/cri.ipynb>`_ # noqa
References
----------
.. [1] http://cie2.nist.gov/TC1-69/NIST%20CQS%20simulation%207.4.xls
(Last accessed 10 June 2014)
"""
from __future__ import division, unicode_literals
import numpy as np
from collections import namedtuple
from colour.colorimetry import STANDARD_OBSERVERS_CMFS
from colour.colorimetry import (
D_illuminant_relative_spd,
blackbody_spd,
spectral_to_XYZ)
from colour.quality.dataset.tcs import TCS_SPDS, TCS_INDEXES_TO_NAMES
from colour.models import UCS_to_uv, XYZ_to_UCS, XYZ_to_xyY
from colour.temperature import CCT_to_xy_illuminant_D, uv_to_CCT_robertson1968
__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__ = ['TSC_COLORIMETRY_DATA_NXYZUVUVW',
'colour_rendering_index']
TSC_COLORIMETRY_DATA_NXYZUVUVW = namedtuple('TscColorimetryData_nXYZuvUVW',
('name', 'XYZ', 'uv', 'UVW'))
def _tcs_colorimetry_data(test_spd,
reference_spd,
tsc_spds,
cmfs,
chromatic_adaptation=False):
"""
Returns the *test colour samples* colorimetry data.
Parameters
----------
test_spd : SpectralPowerDistribution
Test spectral power distribution.
reference_spd : SpectralPowerDistribution
Reference spectral power distribution.
tsc_spds : dict
Test colour samples.
cmfs : XYZ_ColourMatchingFunctions
Standard observer colour matching functions.
chromatic_adaptation : bool, optional
Perform chromatic adaptation.
Returns
-------
list
*Test colour samples* colorimetry data.
"""
test_XYZ = spectral_to_XYZ(test_spd, cmfs)
test_uv = np.ravel(UCS_to_uv(XYZ_to_UCS(test_XYZ)))
test_u, test_v = test_uv[0], test_uv[1]
reference_XYZ = spectral_to_XYZ(reference_spd, cmfs)
reference_uv = np.ravel(UCS_to_uv(XYZ_to_UCS(reference_XYZ)))
reference_u, reference_v = reference_uv[0], reference_uv[1]
tcs_data = []
for key, value in sorted(TCS_INDEXES_TO_NAMES.items()):
tcs_spd = tsc_spds.get(value)
tcs_XYZ = spectral_to_XYZ(tcs_spd, cmfs, test_spd)
tcs_xyY = np.ravel(XYZ_to_xyY(tcs_XYZ))
tcs_uv = np.ravel(UCS_to_uv(XYZ_to_UCS(tcs_XYZ)))
tcs_u, tcs_v = tcs_uv[0], tcs_uv[1]
if chromatic_adaptation:
c = lambda x, y: (4 - x - 10 * y) / y
d = lambda x, y: (1.708 * y + 0.404 - 1.481 * x) / y
test_c, test_d = c(test_u, test_v), d(test_u, test_v)
reference_c, reference_d = (c(reference_u, reference_v),
d(reference_u, reference_v))
tcs_c, tcs_d = c(tcs_u, tcs_v), d(tcs_u, tcs_v)
tcs_u = ((10.872 + 0.404 * reference_c / test_c * tcs_c - 4 *
reference_d / test_d * tcs_d) /
(16.518 + 1.481 * reference_c / test_c * tcs_c -
reference_d / test_d * tcs_d))
tcs_v = (5.52 / (16.518 + 1.481 * reference_c / test_c * tcs_c -
reference_d / test_d * tcs_d))
tcs_W = 25 * tcs_xyY[-1] ** (1 / 3) - 17
tcs_U = 13 * tcs_W * (tcs_u - reference_u)
tcs_V = 13 * tcs_W * (tcs_v - reference_v)
tcs_data.append(
TSC_COLORIMETRY_DATA_NXYZUVUVW(tcs_spd.name,
tcs_XYZ,
tcs_uv,
np.array([tcs_U, tcs_V, tcs_W])))
return tcs_data
def _colour_rendering_indexes(test_data, reference_data):
"""
Returns the *test colour samples* rendering indexes.
Parameters
----------
test_data : list
Test data.
reference_data : list
Reference data.
Returns
-------
dict
*Test colour samples* colour rendering indexes.
"""
colour_rendering_indexes = {}
for i in range(len(test_data)):
colour_rendering_indexes[i + 1] = 100 - 4.6 * np.linalg.norm(
reference_data[i].UVW - test_data[i].UVW)
return colour_rendering_indexes
[docs]def colour_rendering_index(test_spd, additional_data=False):
"""
Returns the *colour rendering index* of given spectral power distribution.
Parameters
----------
test_spd : SpectralPowerDistribution
Test spectral power distribution.
additional_data : bool, optional
Output additional data.
Returns
-------
numeric or (numeric, dict)
Colour rendering index, Tsc data.
Examples
--------
>>> from colour import ILLUMINANTS_RELATIVE_SPDS
>>> spd = ILLUMINANTS_RELATIVE_SPDS.get('F2')
>>> colour_rendering_index(spd) # doctest: +ELLIPSIS
64.1507331...
"""
cmfs = STANDARD_OBSERVERS_CMFS.get('CIE 1931 2 Degree Standard Observer')
shape = cmfs.shape
test_spd = test_spd.clone().align(shape)
tcs_spds = {}
for index, tcs_spd in sorted(TCS_SPDS.items()):
tcs_spds[index] = tcs_spd.clone().align(shape)
XYZ = spectral_to_XYZ(test_spd, cmfs)
uv = UCS_to_uv(XYZ_to_UCS(XYZ))
CCT, Duv = uv_to_CCT_robertson1968(uv)
if CCT < 5000:
reference_spd = blackbody_spd(CCT, shape)
else:
xy = CCT_to_xy_illuminant_D(CCT)
reference_spd = D_illuminant_relative_spd(xy)
reference_spd.align(shape)
test_tcs_colorimetry_data = _tcs_colorimetry_data(
test_spd,
reference_spd,
tcs_spds,
cmfs,
chromatic_adaptation=True)
reference_tcs_colorimetry_data = _tcs_colorimetry_data(
reference_spd,
reference_spd,
tcs_spds, cmfs)
colour_rendering_indexes = _colour_rendering_indexes(
test_tcs_colorimetry_data, reference_tcs_colorimetry_data)
colour_rendering_index = np.average(
[v for k, v in colour_rendering_indexes.items()
if k in (1, 2, 3, 4, 5, 6, 7, 8)])
if additional_data:
return (colour_rendering_index,
colour_rendering_indexes,
[test_tcs_colorimetry_data, reference_tcs_colorimetry_data])
else:
return colour_rendering_index
Colour 0.3