#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
CAM02-LCD, CAM02-SCD, and CAM02-UCS Colourspaces - Luo, Cui and Li (2006)
=========================================================================
Defines the *Luo et al. (2006)* *CAM02-LCD*, *CAM02-SCD*, and *CAM02-UCS*
colourspaces transformations:
- :func:`JMh_CIECAM02_to_CAM02LCD`
- :func:`CAM02LCD_to_JMh_CIECAM02`
- :func:`JMh_CIECAM02_to_CAM02SCD`
- :func:`CAM02SCD_to_JMh_CIECAM02`
- :func:`JMh_CIECAM02_to_CAM02UCS`
- :func:`CAM02UCS_to_JMh_CIECAM02`
See Also
--------
`CAM02-LCD, CAM02-SCD, and CAM02-UCS Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/ucs_luo2006.ipynb>`_
References
----------
.. [1] Luo, R. M., Cui, G., & Li, C. (2006). Uniform Colour Spaces Based on
CIECAM02 Colour Appearance Model. Color Research and Application,
31(4), 320–330. doi:10.1002/col.20227
"""
from __future__ import division, unicode_literals
import numpy as np
from collections import namedtuple
from functools import partial
from colour.algebra import cartesian_to_polar, polar_to_cartesian
from colour.utilities import CaseInsensitiveMapping, tsplit, tstack
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2017 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = [
'Coefficients_UCS_Luo2006', 'COEFFICIENTS_UCS_LUO2006',
'JMh_CIECAM02_to_UCS_Luo2006', 'UCS_Luo2006_to_JMh_CIECAM02',
'JMh_CIECAM02_to_CAM02LCD', 'CAM02LCD_to_JMh_CIECAM02',
'JMh_CIECAM02_to_CAM02SCD', 'CAM02SCD_to_JMh_CIECAM02',
'JMh_CIECAM02_to_CAM02UCS', 'CAM02UCS_to_JMh_CIECAM02'
]
[docs]class Coefficients_UCS_Luo2006(
namedtuple('Coefficients_UCS_Luo2006', ('K_L', 'c_1', 'c_2'))):
"""
Defines the the class storing *Luo et al. (2006)* fitting coefficients for
the *CAM02-LCD*, *CAM02-SCD*, and *CAM02-UCS* colourspaces.
"""
COEFFICIENTS_UCS_LUO2006 = CaseInsensitiveMapping({
'CAM02-LCD': Coefficients_UCS_Luo2006(0.77, 0.007, 0.0053),
'CAM02-SCD': Coefficients_UCS_Luo2006(1.24, 0.007, 0.0363),
'CAM02-UCS': Coefficients_UCS_Luo2006(1.00, 0.007, 0.0228)
})
"""
*Luo et al. (2006)* fitting coefficients for the *CAM02-LCD*, *CAM02-SCD*, and
*CAM02-UCS* colourspaces.
COEFFICIENTS_UCS_LUO2006 : CaseInsensitiveMapping
**{'CAM02-LCD', 'CAM02-SCD', 'CAM02-UCS'}**
"""
[docs]def JMh_CIECAM02_to_UCS_Luo2006(JMh, coefficients):
"""
Converts from *CIECAM02* :math:`JMh` correlates array to one of the
*Luo et al. (2006)* *CAM02-LCD*, *CAM02-SCD*, or *CAM02-UCS* colourspaces
:math:`J'a'b'` array.
The :math:`JMh` correlates array is constructed using the CIECAM02
correlate of *Lightness* :math:`J`, the *CIECAM02* correlate of
*colourfulness* :math:`M` and the *CIECAM02* *Hue* angle :math:`h` in
degrees.
Parameters
----------
JMh : array_like
*CIECAM02* correlates array :math:`JMh`.
coefficients : array_like
Coefficients of one of the *Luo et al. (2006)* *CAM02-LCD*,
*CAM02-SCD*, or *CAM02-UCS* colourspaces.
Returns
-------
ndarray
*Luo et al. (2006)* *CAM02-LCD*, *CAM02-SCD*, or *CAM02-UCS*
colourspaces :math:`J'a'b'` array.
Examples
--------
>>> from colour.appearance import (
... CIECAM02_VIEWING_CONDITIONS,
... XYZ_to_CIECAM02)
>>> XYZ = np.array([19.01, 20.00, 21.78])
>>> XYZ_w = np.array([95.05, 100.00, 108.88])
>>> L_A = 318.31
>>> Y_b = 20.0
>>> surround = CIECAM02_VIEWING_CONDITIONS['Average']
>>> specification = XYZ_to_CIECAM02(
... XYZ, XYZ_w, L_A, Y_b, surround)
>>> JMh = (specification.J, specification.M, specification.h)
>>> JMh_CIECAM02_to_UCS_Luo2006( # doctest: +ELLIPSIS
... JMh, COEFFICIENTS_UCS_LUO2006['CAM02-LCD'])
array([ 54.9043313..., -0.0845039..., -0.0685483...])
"""
J, M, h = tsplit(JMh)
_K_L, c_1, c_2 = tsplit(coefficients)
J_p = ((1 + 100 * c_1) * J) / (1 + c_1 * J)
M_p = (1 / c_2) * np.log(1 + c_2 * M)
a_p, b_p = tsplit(polar_to_cartesian(tstack((M_p, np.radians(h)))))
return tstack((J_p, a_p, b_p))
[docs]def UCS_Luo2006_to_JMh_CIECAM02(Jpapbp, coefficients):
"""
Converts from one of the *Luo et al. (2006)* *CAM02-LCD*, *CAM02-SCD*, or
*CAM02-UCS* colourspaces :math:`J'a'b'` array to *CIECAM02* :math:`JMh`
correlates array.
Parameters
----------
Jpapbp : array_like
*Luo et al. (2006)* *CAM02-LCD*, *CAM02-SCD*, or *CAM02-UCS*
colourspaces :math:`J'a'b'` array.
coefficients : array_like
Coefficients of one of the *Luo et al. (2006)* *CAM02-LCD*,
*CAM02-SCD*, or *CAM02-UCS* colourspaces.
Returns
-------
ndarray
*CIECAM02* correlates array :math:`JMh`.
Examples
--------
>>> Jpapbp = np.array([54.90433134, -0.08450395, -0.06854831])
>>> UCS_Luo2006_to_JMh_CIECAM02( # doctest: +ELLIPSIS
... Jpapbp, COEFFICIENTS_UCS_LUO2006['CAM02-LCD'])
array([ 4.1731091...e+01, 1.0884217...e-01, 2.1904843...e+02])
"""
J_p, a_p, b_p = tsplit(Jpapbp)
_K_L, c_1, c_2 = tsplit(coefficients)
J = -J_p / (c_1 * J_p - 1 - 100 * c_1)
M_p, h = tsplit(cartesian_to_polar(tstack((a_p, b_p))))
M = (np.exp(M_p / (1 / c_2)) - 1) / c_2
return tstack((J, M, np.degrees(h) % 360))
JMh_CIECAM02_to_CAM02LCD = partial(
JMh_CIECAM02_to_UCS_Luo2006,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-LCD'])
CAM02LCD_to_JMh_CIECAM02 = partial(
UCS_Luo2006_to_JMh_CIECAM02,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-LCD'])
JMh_CIECAM02_to_CAM02SCD = partial(
JMh_CIECAM02_to_UCS_Luo2006,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-SCD'])
CAM02SCD_to_JMh_CIECAM02 = partial(
UCS_Luo2006_to_JMh_CIECAM02,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-SCD'])
JMh_CIECAM02_to_CAM02UCS = partial(
JMh_CIECAM02_to_UCS_Luo2006,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-UCS'])
CAM02UCS_to_JMh_CIECAM02 = partial(
UCS_Luo2006_to_JMh_CIECAM02,
coefficients=COEFFICIENTS_UCS_LUO2006['CAM02-UCS'])