"""
Fairchild (1990) Chromatic Adaptation Model
===========================================
Define the *Fairchild (1990)* chromatic adaptation model objects:
- :func:`colour.adaptation.chromatic_adaptation_Fairchild1990`
References
----------
- :cite:`Fairchild1991a` : Fairchild, M. D. (1991). Formulation and testing
of an incomplete-chromatic-adaptation model. Color Research & Application,
16(4), 243-250. doi:10.1002/col.5080160406
- :cite:`Fairchild2013s` : Fairchild, M. D. (2013). FAIRCHILD'S 1990 MODEL.
In Color Appearance Models (3rd ed., pp. 4418-4495). Wiley. ISBN:B00DAYO8E2
"""
from __future__ import annotations
import typing
import numpy as np
from colour.adaptation import CAT_VON_KRIES
from colour.algebra import sdiv, sdiv_mode, spow, vecmul
if typing.TYPE_CHECKING:
from colour.hints import ArrayLike, NDArrayFloat
from colour.utilities import (
as_float_array,
from_range_100,
ones,
row_as_diagonal,
to_domain_100,
tstack,
)
__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 Colour Developers"
__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Production"
__all__ = [
"MATRIX_XYZ_TO_RGB_FAIRCHILD1990",
"MATRIX_RGB_TO_XYZ_FAIRCHILD1990",
"chromatic_adaptation_Fairchild1990",
"XYZ_to_RGB_Fairchild1990",
"RGB_to_XYZ_Fairchild1990",
"degrees_of_adaptation",
]
MATRIX_XYZ_TO_RGB_FAIRCHILD1990: NDArrayFloat = CAT_VON_KRIES
"""
*Fairchild (1990)* colour appearance model *CIE XYZ* tristimulus values to cone
responses matrix.
"""
MATRIX_RGB_TO_XYZ_FAIRCHILD1990: NDArrayFloat = np.linalg.inv(CAT_VON_KRIES)
"""
*Fairchild (1990)* colour appearance model cone responses to *CIE XYZ*
tristimulus values matrix.
"""
[docs]
def chromatic_adaptation_Fairchild1990(
XYZ_1: ArrayLike,
XYZ_n: ArrayLike,
XYZ_r: ArrayLike,
Y_n: ArrayLike,
discount_illuminant: bool = False,
) -> NDArrayFloat:
"""
Adapt given stimulus *CIE XYZ_1* tristimulus values from test viewing
conditions to reference viewing conditions using *Fairchild (1990)*
chromatic adaptation model.
Parameters
----------
XYZ_1
*CIE XYZ_1* tristimulus values of test sample / stimulus.
XYZ_n
Test viewing condition *CIE XYZ_n* tristimulus values of whitepoint.
XYZ_r
Reference viewing condition *CIE XYZ_r* tristimulus values of
whitepoint.
Y_n
Luminance :math:`Y_n` of test adapting stimulus in :math:`cd/m^2`.
discount_illuminant
Truth value indicating if the illuminant should be discounted.
Returns
-------
:class:`numpy.ndarray`
Adapted *CIE XYZ_2* tristimulus values of stimulus.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``XYZ_1`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
| ``XYZ_n`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
| ``XYZ_r`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``XYZ_2`` | [0, 100] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Fairchild1991a`, :cite:`Fairchild2013s`
Examples
--------
>>> XYZ_1 = np.array([19.53, 23.07, 24.97])
>>> XYZ_n = np.array([111.15, 100.00, 35.20])
>>> XYZ_r = np.array([94.81, 100.00, 107.30])
>>> Y_n = 200
>>> chromatic_adaptation_Fairchild1990(XYZ_1, XYZ_n, XYZ_r, Y_n)
... # doctest: +ELLIPSIS
array([ 23.3252634..., 23.3245581..., 76.1159375...])
"""
XYZ_1 = to_domain_100(XYZ_1)
XYZ_n = to_domain_100(XYZ_n)
XYZ_r = to_domain_100(XYZ_r)
Y_n = as_float_array(Y_n)
LMS_1 = vecmul(MATRIX_XYZ_TO_RGB_FAIRCHILD1990, XYZ_1)
LMS_n = vecmul(MATRIX_XYZ_TO_RGB_FAIRCHILD1990, XYZ_n)
LMS_r = vecmul(MATRIX_XYZ_TO_RGB_FAIRCHILD1990, XYZ_r)
p_LMS = degrees_of_adaptation(LMS_1, Y_n, discount_illuminant=discount_illuminant)
a_LMS_1 = p_LMS / LMS_n
a_LMS_2 = p_LMS / LMS_r
A_1 = row_as_diagonal(a_LMS_1)
A_2 = row_as_diagonal(a_LMS_2)
LMSp_1 = vecmul(A_1, LMS_1)
c = 0.219 - 0.0784 * np.log10(Y_n)
C = row_as_diagonal(tstack([c, c, c]))
LMS_a = vecmul(C, LMSp_1)
LMSp_2 = vecmul(np.linalg.inv(C), LMS_a)
LMS_c = vecmul(np.linalg.inv(A_2), LMSp_2)
XYZ_c = vecmul(MATRIX_RGB_TO_XYZ_FAIRCHILD1990, LMS_c)
return from_range_100(XYZ_c)
def XYZ_to_RGB_Fairchild1990(XYZ: ArrayLike) -> NDArrayFloat:
"""
Convert from *CIE XYZ* tristimulus values to cone responses.
Parameters
----------
XYZ
*CIE XYZ* tristimulus values.
Returns
-------
:class:`numpy.ndarray`
Cone responses.
Examples
--------
>>> XYZ = np.array([19.53, 23.07, 24.97])
>>> XYZ_to_RGB_Fairchild1990(XYZ) # doctest: +ELLIPSIS
array([ 22.1231935..., 23.6054224..., 22.9279534...])
"""
return vecmul(MATRIX_XYZ_TO_RGB_FAIRCHILD1990, XYZ)
def RGB_to_XYZ_Fairchild1990(RGB: ArrayLike) -> NDArrayFloat:
"""
Convert from cone responses to *CIE XYZ* tristimulus values.
Parameters
----------
RGB
Cone responses.
Returns
-------
:class:`numpy.ndarray`
*CIE XYZ* tristimulus values.
Examples
--------
>>> RGB = np.array([22.12319350, 23.60542240, 22.92795340])
>>> RGB_to_XYZ_Fairchild1990(RGB) # doctest: +ELLIPSIS
array([ 19.53, 23.07, 24.97])
"""
return vecmul(MATRIX_RGB_TO_XYZ_FAIRCHILD1990, RGB)
def degrees_of_adaptation(
LMS: ArrayLike,
Y_n: ArrayLike,
v: ArrayLike = 1 / 3,
discount_illuminant: bool = False,
) -> NDArrayFloat:
"""
Compute the degrees of adaptation :math:`p_L`, :math:`p_M` and
:math:`p_S`.
Parameters
----------
LMS
Cone responses.
Y_n
Luminance :math:`Y_n` of test adapting stimulus in :math:`cd/m^2`.
v
Exponent :math:`v`.
discount_illuminant
Truth value indicating if the illuminant should be discounted.
Returns
-------
:class:`numpy.ndarray`
Degrees of adaptation :math:`p_L`, :math:`p_M` and :math:`p_S`.
Examples
--------
>>> LMS = np.array([20.00052060, 19.99978300, 19.99883160])
>>> Y_n = 31.83
>>> degrees_of_adaptation(LMS, Y_n) # doctest: +ELLIPSIS
array([ 0.9799324..., 0.9960035..., 1.0233041...])
>>> degrees_of_adaptation(LMS, Y_n, 1 / 3, True)
array([ 1., 1., 1.])
"""
LMS = as_float_array(LMS)
if discount_illuminant:
return ones(LMS.shape)
Y_n = as_float_array(Y_n)
v = as_float_array(v)
# E illuminant.
LMS_E = vecmul(CAT_VON_KRIES, ones(LMS.shape))
Ye_n = spow(Y_n, v)
def m_E(x: NDArrayFloat, y: NDArrayFloat) -> NDArrayFloat:
"""Compute the :math:`m_E` term."""
return (3 * x / y) / np.sum(x / y, axis=-1)[..., None]
def P_c(x: NDArrayFloat) -> NDArrayFloat:
"""Compute the :math:`P_L`, :math:`P_M` or :math:`P_S` terms."""
return sdiv(
1 + Ye_n[..., None] + x,
1 + Ye_n[..., None] + sdiv(1, x),
)
with sdiv_mode():
return P_c(m_E(LMS, LMS_E))
