#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Munsell Renotation System
=========================
Defines various objects for *Munsell Renotation System* computations:
- :func:`munsell_value_Priest1920`: *Munsell* value :math:`V` computation of
given *luminance* :math:`Y` using Priest, Gibson and MacNicholas (1920)
method.
- :func:`munsell_value_Munsell1933`: *Munsell* value :math:`V` computation of
given *luminance* :math:`Y` using Munsell, Sloan and Godlove (1933)
method.
- :func:`munsell_value_Moon1943`: *Munsell* value :math:`V` computation of
given *luminance* :math:`Y` using Moon and Spencer (1943) method.
- :func:`munsell_value_Saunderson1944`: *Munsell* value :math:`V` computation
of given *luminance* :math:`Y` using Saunderson and Milner (1944) method.
- :func:`munsell_value_Ladd1955`: *Munsell* value :math:`V` computation of
given *luminance* :math:`Y` using Ladd and Pinney (1955) method.
- :func:`munsell_value_McCamy1987`: *Munsell* value :math:`V` computation of
given *luminance* :math:`Y` using McCamy (1987) method.
- :func:`munsell_value_ASTMD153508` [1]_ [2]_: *Munsell* value :math:`V`
computation of given *luminance* :math:`Y` using ASTM D1535-08e1 (2008)
method.
- :func:`munsell_colour_to_xyY` [1]_ [2]_
- :func:`xyY_to_munsell_colour` [1]_ [2]_
See Also
--------
`Munsell Renotation System IPython Notebook
<http://nbviewer.ipython.org/github/colour-science/colour-ipython/blob/master/notebooks/notation/munsell.ipynb>`_ # noqa
References
----------
.. [1] Centore, P. (n.d.). Munsell Resources. Retrieved July 26, 2014, from
http://www.99main.com/~centore/MunsellResources/MunsellResources.html
.. [2] Centore, P. (2012). An open-source inversion algorithm for the Munsell
renotation. Color Research & Application, 37(6), 455–464.
doi:10.1002/col.20715
"""
from __future__ import division, unicode_literals
import numpy as np
import re
try:
from collections import OrderedDict
except ImportError:
from ordereddict import OrderedDict
from colour.algebra import (
Extrapolator1d,
LinearInterpolator,
cartesian_to_cylindrical)
from colour.colorimetry import ILLUMINANTS, luminance_ASTMD153508
from colour.constants import (
INTEGER_THRESHOLD,
FLOATING_POINT_NUMBER_PATTERN)
from colour.models import Lab_to_LCHab, XYZ_to_Lab, XYZ_to_xy, xyY_to_XYZ
from colour.volume import is_within_macadam_limits
from colour.notation import MUNSELL_COLOURS_ALL
from colour.utilities import (
CaseInsensitiveMapping,
Lookup,
is_integer,
is_numeric)
__author__ = 'Colour Developers, Paul Centore'
__copyright__ = 'Copyright (C) 2013 - 2015 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = ['MUNSELL_GRAY_PATTERN',
'MUNSELL_COLOUR_PATTERN',
'MUNSELL_GRAY_FORMAT',
'MUNSELL_COLOUR_FORMAT',
'MUNSELL_GRAY_EXTENDED_FORMAT',
'MUNSELL_COLOUR_EXTENDED_FORMAT',
'MUNSELL_HUE_LETTER_CODES',
'MUNSELL_DEFAULT_ILLUMINANT',
'MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES',
'munsell_value_Priest1920',
'munsell_value_Munsell1933',
'munsell_value_Moon1943',
'munsell_value_Saunderson1944',
'munsell_value_Ladd1955',
'munsell_value_McCamy1987',
'munsell_value_ASTMD153508',
'MUNSELL_VALUE_METHODS',
'munsell_value',
'munsell_specification_to_xyY',
'munsell_colour_to_xyY',
'xyY_to_munsell_specification',
'xyY_to_munsell_colour',
'parse_munsell_colour',
'is_grey_munsell_colour',
'normalize_munsell_specification',
'munsell_colour_to_munsell_specification',
'munsell_specification_to_munsell_colour',
'xyY_from_renotation',
'is_specification_in_renotation',
'bounding_hues_from_renotation',
'hue_to_hue_angle',
'hue_angle_to_hue',
'hue_to_ASTM_hue',
'interpolation_method_from_renotation_ovoid',
'xy_from_renotation_ovoid',
'LCHab_to_munsell_specification',
'maximum_chroma_from_renotation',
'munsell_specification_to_xy']
MUNSELL_GRAY_PATTERN = 'N(?P<value>{0})'.format(FLOATING_POINT_NUMBER_PATTERN)
MUNSELL_COLOUR_PATTERN = (
'(?P<hue>{0})\s*'
'(?P<letter>BG|GY|YR|RP|PB|B|G|Y|R|P)\s*'
'(?P<value>{0})\s*\/\s*(?P<chroma>[-+]?{0})'.format(
FLOATING_POINT_NUMBER_PATTERN))
MUNSELL_GRAY_FORMAT = 'N{0}'
MUNSELL_COLOUR_FORMAT = '{0} {1}/{2}'
MUNSELL_GRAY_EXTENDED_FORMAT = 'N{0:.{1}f}'
MUNSELL_COLOUR_EXTENDED_FORMAT = '{0:.{1}f}{2} {3:.{4}f}/{5:.{6}f}'
MUNSELL_HUE_LETTER_CODES = Lookup({
'BG': 2,
'GY': 4,
'YR': 6,
'RP': 8,
'PB': 10,
'B': 1,
'G': 3,
'Y': 5,
'R': 7,
'P': 9})
MUNSELL_DEFAULT_ILLUMINANT = 'C'
MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES = ILLUMINANTS.get(
'CIE 1931 2 Degree Standard Observer').get(
MUNSELL_DEFAULT_ILLUMINANT)
_MUNSELL_SPECIFICATIONS_CACHE = None
_MUNSELL_VALUE_ASTM_D1535_08_INTERPOLATOR_CACHE = None
_MUNSELL_MAXIMUM_CHROMAS_FROM_RENOTATION_CACHE = None
def _munsell_specifications():
"""
Returns the *Munsell Renotation System* specifications and caches them if
not existing.
The *Munsell Renotation System* data is stored in
:attr:`colour.notation.dataset.munsell.MUNSELL_COLOURS` attribute in a 2
columns form:
(('2.5GY', 0.2, 2.0), (0.713, 1.414, 0.237)),
(('5GY', 0.2, 2.0), (0.449, 1.145, 0.237)),
(('7.5GY', 0.2, 2.0), (0.262, 0.837, 0.237)),
...,)
The first column is converted from *Munsell* colour to specification using
:func:`munsell_colour_to_munsell_specification` definition:
('2.5GY', 0.2, 2.0) ---> (2.5, 0.2, 2.0, 4)
Returns
-------
list
*Munsell Renotation System* specifications.
"""
global _MUNSELL_SPECIFICATIONS_CACHE
if _MUNSELL_SPECIFICATIONS_CACHE is None:
_MUNSELL_SPECIFICATIONS_CACHE = [
munsell_colour_to_munsell_specification(
MUNSELL_COLOUR_FORMAT.format(*colour[0]))
for colour in MUNSELL_COLOURS_ALL]
return _MUNSELL_SPECIFICATIONS_CACHE
def _munsell_value_ASTMD153508_interpolator():
"""
Returns the *Munsell* value interpolator for ASTM D1535-08e1 (2008) method
and caches it if not existing.
Returns
-------
Extrapolator1d
*Munsell* value interpolator for ASTM D1535-08e1 (2008) method.
"""
global _MUNSELL_VALUE_ASTM_D1535_08_INTERPOLATOR_CACHE
munsell_values = np.arange(0, 10, 0.001)
if _MUNSELL_VALUE_ASTM_D1535_08_INTERPOLATOR_CACHE is None:
_MUNSELL_VALUE_ASTM_D1535_08_INTERPOLATOR_CACHE = Extrapolator1d(
LinearInterpolator(
luminance_ASTMD153508(munsell_values),
munsell_values))
return _MUNSELL_VALUE_ASTM_D1535_08_INTERPOLATOR_CACHE
def _munsell_maximum_chromas_from_renotation():
"""
Returns the maximum *Munsell* chromas from *Munsell Renotation System* data
and caches them if not existing.
Returns
-------
tuple
Maximum *Munsell* chromas.
"""
global _MUNSELL_MAXIMUM_CHROMAS_FROM_RENOTATION_CACHE
if _MUNSELL_MAXIMUM_CHROMAS_FROM_RENOTATION_CACHE is None:
chromas = OrderedDict()
for munsell_colour in MUNSELL_COLOURS_ALL:
hue, value, chroma, code = munsell_colour_to_munsell_specification(
MUNSELL_COLOUR_FORMAT.format(*munsell_colour[0]))
index = (hue, value, code)
if index in chromas:
chroma = max(chromas[index], chroma)
chromas[index] = chroma
_MUNSELL_MAXIMUM_CHROMAS_FROM_RENOTATION_CACHE = tuple(
zip(chromas.keys(), chromas.values()))
return _MUNSELL_MAXIMUM_CHROMAS_FROM_RENOTATION_CACHE
[docs]def munsell_value_Priest1920(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
*Priest, Gibson and MacNicholas (1920)* method.
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
References
----------
.. [3] Wikipedia. (n.d.). Lightness. Retrieved April 13, 2014, from
http://en.wikipedia.org/wiki/Lightness
Examples
--------
>>> munsell_value_Priest1920(10.08) # doctest: +ELLIPSIS
3.1749015...
"""
Y = np.asarray(Y)
V = 10 * np.sqrt(Y / 100)
return V
[docs]def munsell_value_Munsell1933(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
*Munsell, Sloan and Godlove (1933)* method. [3]_
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value_Munsell1933(10.08) # doctest: +ELLIPSIS
3.7918355...
"""
Y = np.asarray(Y)
V = np.sqrt(1.4742 * Y - 0.004743 * (Y * Y))
return V
[docs]def munsell_value_Moon1943(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
Moon and Spencer (1943) method. [3]_
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value_Moon1943(10.08) # doctest: +ELLIPSIS
3.7462971...
"""
Y = np.asarray(Y)
V = 1.4 * Y ** 0.426
return V
[docs]def munsell_value_Saunderson1944(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
Saunderson and Milner (1944) method. [3]_
Parameters
----------
Y : numeric
*luminance* :math:`Y`.
Returns
-------
numeric
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value_Saunderson1944(10.08) # doctest: +ELLIPSIS
3.6865080...
"""
Y = np.asarray(Y)
V = 2.357 * (Y ** 0.343) - 1.52
return V
[docs]def munsell_value_Ladd1955(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
Ladd and Pinney (1955) method. [3]_
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value_Ladd1955(10.08) # doctest: +ELLIPSIS
3.6952862...
"""
Y = np.asarray(Y)
V = 2.468 * (Y ** (1 / 3)) - 1.636
return V
[docs]def munsell_value_McCamy1987(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
McCamy (1987) method.
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
References
----------
.. [4] ASTM International. (1989). ASTM D1535-89 Standard Test Method for
Specifying Color by the Munsell System. Retrieved from
http://www.astm.org/DATABASE.CART/HISTORICAL/D1535-89.htm
Examples
--------
>>> munsell_value_McCamy1987(10.08) # doctest: +ELLIPSIS
array(3.7347235...)
"""
Y = np.asarray(Y)
V = np.where(Y <= 0.9,
0.87445 * (Y ** 0.9967),
(2.49268 * (Y ** (1 / 3)) - 1.5614 -
(0.985 / (((0.1073 * Y - 3.084) ** 2) + 7.54)) +
(0.0133 / (Y ** 2.3)) +
0.0084 * np.sin(4.1 * (Y ** (1 / 3)) + 1) +
(0.0221 / Y) * np.sin(0.39 * (Y - 2)) -
(0.0037 / (0.44 * Y)) * np.sin(1.28 * (Y - 0.53))))
return V
[docs]def munsell_value_ASTMD153508(Y):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
a reverse lookup table from ASTM D1535-08e1 (2008) method.
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value_ASTMD153508(10.1488096782) # doctest: +ELLIPSIS
3.7462971...
"""
Y = np.asarray(Y)
V = _munsell_value_ASTMD153508_interpolator()(Y)
return V
MUNSELL_VALUE_METHODS = CaseInsensitiveMapping(
{'Priest 1920': munsell_value_Priest1920,
'Munsell 1933': munsell_value_Munsell1933,
'Moon 1943': munsell_value_Moon1943,
'Saunderson 1944': munsell_value_Saunderson1944,
'Ladd 1955': munsell_value_Ladd1955,
'McCamy 1987': munsell_value_McCamy1987,
'ASTM D1535-08': munsell_value_ASTMD153508})
"""
Supported *Munsell* value computations methods.
MUNSELL_VALUE_METHODS : CaseInsensitiveMapping
**{'Priest 1920', 'Munsell 1933', 'Moon 1943', 'Saunderson 1944',
'Ladd 1955', 'McCamy 1987', 'ASTM D1535-08'}**
Aliases:
- 'astm2008': 'ASTM D1535-08'
"""
MUNSELL_VALUE_METHODS['astm2008'] = (
MUNSELL_VALUE_METHODS['ASTM D1535-08'])
[docs]def munsell_value(Y, method='ASTM D1535-08'):
"""
Returns the *Munsell* value :math:`V` of given *luminance* :math:`Y` using
given method.
Parameters
----------
Y : numeric or array_like
*luminance* :math:`Y`.
method : unicode, optional
**{'ASTM D1535-08', 'Priest 1920', 'Munsell 1933', 'Moon 1943',
'Saunderson 1944', 'Ladd 1955', 'McCamy 1987'}**,
Computation method.
Returns
-------
numeric or ndarray
*Munsell* value :math:`V`.
Notes
-----
- Input *Y* is in domain [0, 100].
- Output *V* is in domain [0, 10].
Examples
--------
>>> munsell_value(10.08) # doctest: +ELLIPSIS
3.7344764...
>>> munsell_value(10.08, method='Priest 1920') # doctest: +ELLIPSIS
3.1749015...
>>> munsell_value(10.08, method='Munsell 1933') # doctest: +ELLIPSIS
3.7918355...
>>> munsell_value(10.08, method='Moon 1943') # doctest: +ELLIPSIS
3.7462971...
>>> munsell_value(10.08, method='Saunderson 1944') # doctest: +ELLIPSIS
3.6865080...
>>> munsell_value(10.08, method='Ladd 1955') # doctest: +ELLIPSIS
3.6952862...
>>> munsell_value(10.08, method='McCamy 1987') # doctest: +ELLIPSIS
array(3.7347235...)
"""
return MUNSELL_VALUE_METHODS.get(method)(Y)
[docs]def munsell_specification_to_xyY(specification):
"""
Converts given *Munsell* *Colorlab* specification to *CIE xyY* colourspace.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
ndarray, (3,)
*CIE xyY* colourspace array.
Notes
-----
- Input *Munsell* *Colorlab* specification hue must be in domain [0, 10].
- Input *Munsell* *Colorlab* specification value must be in domain
[0, 10].
- Output *CIE xyY* colourspace array is in domain [0, 1].
References
----------
.. [5] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/MunsellToxyY.m. Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> spc = (2.1, 8.0, 17.9, 4)
>>> munsell_specification_to_xyY(spc) # doctest: +ELLIPSIS
array([ 0.4400632..., 0.5522428..., 0.5761962...])
>>> munsell_specification_to_xyY(8.9) # doctest: +ELLIPSIS
array([ 0.31006 , 0.31616 , 0.746134...])
"""
if is_grey_munsell_colour(specification):
value = specification
else:
hue, value, chroma, code = specification
assert 0 <= hue <= 10, (
'"{0}" specification hue must be in domain [0, 10]!'.format(
specification))
assert 0 <= value <= 10, (
'"{0}" specification value must be in domain [0, 10]!'.format(
specification))
Y = luminance_ASTMD153508(value)
if is_integer(value):
value_minus = value_plus = round(value)
else:
value_minus = np.floor(value)
value_plus = value_minus + 1
specification_minus = (value_minus
if is_grey_munsell_colour(specification) else
(hue, value_minus, chroma, code))
x_minus, y_minus = munsell_specification_to_xy(specification_minus)
plus_specification = (value_plus
if (is_grey_munsell_colour(specification) or
value_plus == 10) else
(hue, value_plus, chroma, code))
x_plus, y_plus = munsell_specification_to_xy(plus_specification)
if value_minus == value_plus:
x = x_minus
y = y_minus
else:
Y_minus = luminance_ASTMD153508(value_minus)
Y_plus = luminance_ASTMD153508(value_plus)
x = LinearInterpolator((Y_minus, Y_plus), (x_minus, x_plus))(Y)
y = LinearInterpolator((Y_minus, Y_plus), (y_minus, y_plus))(Y)
return np.array([x, y, Y / 100])
[docs]def munsell_colour_to_xyY(munsell_colour):
"""
Converts given *Munsell* colour to *CIE xyY* colourspace.
Parameters
----------
munsell_colour : unicode
*Munsell* colour.
Returns
-------
ndarray, (3,)
*CIE xyY* colourspace array.
Notes
-----
- Output *CIE xyY* colourspace array is in domain [0, 1].
Examples
--------
>>> munsell_colour_to_xyY('4.2YR 8.1/5.3') # doctest: +ELLIPSIS
array([ 0.3873694..., 0.3575165..., 0.59362 ])
>>> munsell_colour_to_xyY('N8.9') # doctest: +ELLIPSIS
array([ 0.31006 , 0.31616 , 0.746134...])
"""
specification = munsell_colour_to_munsell_specification(munsell_colour)
return munsell_specification_to_xyY(specification)
[docs]def xyY_to_munsell_specification(xyY):
"""
Converts from *CIE xyY* colourspace to *Munsell* *Colorlab* specification.
Parameters
----------
xyY : array_like, (3,)
*CIE xyY* colourspace array.
Returns
-------
numeric or tuple
*Munsell* *Colorlab* specification.
Raises
------
ValueError
If the given *CIE xyY* colourspace array is not within MacAdam
limits.
RuntimeError
If the maximum iterations count has been reached without converging to
a result.
Notes
-----
- Input *CIE xyY* colourspace array is in domain [0, 1].
References
----------
.. [6] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/xyYtoMunsell.m. Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> xyY = np.array([0.38736945, 0.35751656, 0.59362000])
>>> xyY_to_munsell_specification(xyY) # doctest: +ELLIPSIS
(4.1742530..., 8.0999999..., 5.3044360..., 6)
"""
if not is_within_macadam_limits(xyY, MUNSELL_DEFAULT_ILLUMINANT):
raise ValueError(
('"{0}" is not within "MacAdam" limits for illuminant '
'"{1}"!').format(xyY, MUNSELL_DEFAULT_ILLUMINANT))
x, y, Y = np.ravel(xyY)
# Scaling *Y* for algorithm needs.
value = munsell_value_ASTMD153508(Y * 100)
if is_integer(value):
value = round(value)
x_center, y_center, Y_center = np.ravel(
munsell_specification_to_xyY(value))
_z_input, theta_input, rho_input = cartesian_to_cylindrical((x - x_center,
y - y_center,
Y_center))
theta_input = np.degrees(theta_input)
grey_threshold = 0.001
if rho_input < grey_threshold:
return value
X, Y, Z = np.ravel(xyY_to_XYZ((x, y, Y)))
xi, yi = MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES
Xr, Yr, Zr = np.ravel(xyY_to_XYZ((xi, yi, Y)))
XYZ = np.array([X, Y, Z])
XYZr = np.array([(1 / Yr) * Xr, 1, (1 / Yr) * Zr])
Lab = XYZ_to_Lab(XYZ, XYZ_to_xy(XYZr))
LCHab = Lab_to_LCHab(Lab)
hue_initial, _value_initial, chroma_initial, code_initial = (
LCHab_to_munsell_specification(LCHab))
specification_current = [hue_initial,
value,
(5 / 5.5) * chroma_initial,
code_initial]
convergence_threshold = 0.0001
iterations_maximum = 64
iterations = 0
while iterations <= iterations_maximum:
iterations += 1
hue_current, _value_current, chroma_current, code_current = (
specification_current)
hue_angle_current = hue_to_hue_angle(hue_current, code_current)
chroma_maximum = maximum_chroma_from_renotation(hue_current,
value,
code_current)
if chroma_current > chroma_maximum:
chroma_current = specification_current[2] = chroma_maximum
x_current, y_current, _Y_current = np.ravel(
munsell_specification_to_xyY(specification_current))
_z_current, theta_current, rho_current = cartesian_to_cylindrical(
(x_current - x_center,
y_current - y_center,
Y_center))
theta_current = np.degrees(theta_current)
theta_current_difference = (360 - theta_input + theta_current) % 360
if theta_current_difference > 180:
theta_current_difference -= 360
theta_differences = [theta_current_difference]
hue_angles = [hue_angle_current]
hue_angles_differences = [0]
iterations_maximum_inner = 16
iterations_inner = 0
extrapolate = False
while np.sign(min(theta_differences)) == np.sign(
max(theta_differences)) and extrapolate is False:
iterations_inner += 1
if iterations_inner > iterations_maximum_inner:
raise RuntimeError(('Maximum inner iterations count reached '
'without convergence!'))
hue_angle_inner = ((hue_angle_current + iterations_inner *
(theta_input - theta_current)) % 360)
hue_angle_difference_inner = (iterations_inner *
(theta_input - theta_current) % 360)
if hue_angle_difference_inner > 180:
hue_angle_difference_inner -= 360
hue_inner, code_inner = hue_angle_to_hue(hue_angle_inner)
x_inner, y_inner, _Y_inner = np.ravel(
munsell_specification_to_xyY((hue_inner,
value,
chroma_current,
code_inner)))
if len(theta_differences) >= 2:
extrapolate = True
if extrapolate is False:
_z_inner, theta_inner, rho_inner = cartesian_to_cylindrical(
(x_inner - x_center,
y_inner - y_center,
Y_center))
theta_inner = np.degrees(theta_inner)
theta_inner_difference = (
(360 - theta_input + theta_inner) % 360)
if theta_inner_difference > 180:
theta_inner_difference -= 360
theta_differences.append(theta_inner_difference)
hue_angles.append(hue_angle_inner)
hue_angles_differences.append(hue_angle_difference_inner)
theta_differences = np.array(theta_differences)
hue_angles_differences = np.array(hue_angles_differences)
theta_differences_indexes = theta_differences.argsort()
theta_differences = theta_differences[theta_differences_indexes]
hue_angles_differences = hue_angles_differences[
theta_differences_indexes]
hue_angle_difference_new = Extrapolator1d(
LinearInterpolator(
theta_differences,
hue_angles_differences))(0) % 360
hue_angle_new = (hue_angle_current + hue_angle_difference_new) % 360
hue_new, code_new = hue_angle_to_hue(hue_angle_new)
specification_current = [hue_new, value, chroma_current, code_new]
x_current, y_current, Y_current = np.ravel(
munsell_specification_to_xyY(specification_current))
difference = np.linalg.norm(
np.array([x, y]) - np.array([x_current, y_current]))
if difference < convergence_threshold:
return tuple(specification_current)
# TODO: Consider refactoring implementation.
hue_current, value_current, chroma_current, code_current = (
specification_current)
chroma_maximum = maximum_chroma_from_renotation(hue_current,
value,
code_current)
if chroma_current > chroma_maximum:
chroma_current = specification_current[2] = chroma_maximum
x_current, y_current, Y_current = np.ravel(
munsell_specification_to_xyY(specification_current))
z_current, theta_current, rho_current = cartesian_to_cylindrical(
(x_current - x_center, y_current - y_center, Y_center))
rho_bounds = [rho_current]
chroma_bounds = [chroma_current]
iterations_maximum_inner = 16
iterations_inner = 0
while rho_input < min(rho_bounds) or rho_input > max(rho_bounds):
iterations_inner += 1
if iterations_inner > iterations_maximum_inner:
raise RuntimeError(('Maximum inner iterations count reached '
'without convergence!'))
chroma_inner = (((rho_input / rho_current) ** iterations_inner) *
chroma_current)
if chroma_inner > chroma_maximum:
chroma_inner = specification_current[2] = chroma_maximum
specification_inner = (
hue_current, value, chroma_inner, code_current)
x_inner, y_inner, Y_inner = np.ravel(
munsell_specification_to_xyY(specification_inner))
z_inner, theta_inner, rho_inner = cartesian_to_cylindrical(
(x_inner - x_center, y_inner - y_center, Y_center))
rho_bounds.append(rho_inner)
chroma_bounds.append(chroma_inner)
rho_bounds = np.array(rho_bounds)
chroma_bounds = np.array(chroma_bounds)
rhos_bounds_indexes = rho_bounds.argsort()
rho_bounds = rho_bounds[rhos_bounds_indexes]
chroma_bounds = chroma_bounds[rhos_bounds_indexes]
chroma_new = LinearInterpolator(rho_bounds, chroma_bounds)(rho_input)
specification_current = [hue_current, value, chroma_new, code_current]
x_current, y_current, Y_current = np.ravel(
munsell_specification_to_xyY(specification_current))
difference = np.linalg.norm(
np.array([x, y]) - np.array([x_current, y_current]))
if difference < convergence_threshold:
return tuple(specification_current)
raise RuntimeError(
'Maximum outside iterations count reached without convergence!')
[docs]def xyY_to_munsell_colour(xyY,
hue_decimals=1,
value_decimals=1,
chroma_decimals=1):
"""
Converts from *CIE xyY* colourspace to *Munsell* colour.
Parameters
----------
xyY : array_like, (3,)
*CIE xyY* colourspace array.
hue_decimals : int
Hue formatting decimals.
value_decimals : int
Value formatting decimals.
chroma_decimals : int
Chroma formatting decimals.
Returns
-------
unicode
*Munsell* colour.
Notes
-----
- Input *CIE xyY* colourspace array is in domain [0, 1].
Examples
--------
>>> xyY = np.array([0.38736945, 0.35751656, 0.59362000])
>>> # Doctests skip for Python 2.x compatibility.
>>> xyY_to_munsell_colour(xyY) # doctest: +SKIP
'4.2YR 8.1/5.3'
"""
specification = xyY_to_munsell_specification(xyY)
return munsell_specification_to_munsell_colour(specification,
hue_decimals,
value_decimals,
chroma_decimals)
[docs]def parse_munsell_colour(munsell_colour):
"""
Parses given *Munsell* colour and returns an intermediate *Munsell*
*Colorlab* specification.
Parameters
----------
munsell_colour : unicode
*Munsell* colour.
Returns
-------
float or tuple
Intermediate *Munsell* *Colorlab* specification.
Raises
------
ValueError
If the given specification is not a valid *Munsell Renotation System*
colour specification.
Examples
--------
>>> parse_munsell_colour('N5.2') # doctest: +ELLIPSIS
5.2...
>>> parse_munsell_colour('0YR 2.0/4.0')
(0.0, 2.0, 4.0, 6)
"""
match = re.match(MUNSELL_GRAY_PATTERN,
munsell_colour,
flags=re.IGNORECASE)
if match:
return float(match.group('value'))
match = re.match(MUNSELL_COLOUR_PATTERN,
munsell_colour,
flags=re.IGNORECASE)
if match:
return (float(match.group('hue')),
float(match.group('value')),
float(match.group('chroma')),
MUNSELL_HUE_LETTER_CODES.get(match.group('letter').upper()))
raise ValueError(
('"{0}" is not a valid "Munsell Renotation System" colour '
'specification!').format(munsell_colour))
[docs]def is_grey_munsell_colour(specification):
"""
Returns if given *Munsell* *Colorlab* specification is a single number form
used for grey colour.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
bool
Is specification a grey colour.
Examples
--------
>>> is_grey_munsell_colour((0.0, 2.0, 4.0, 6))
False
>>> is_grey_munsell_colour(0.5)
True
"""
return is_numeric(specification)
[docs]def normalize_munsell_specification(specification):
"""
Normalises given *Munsell* *Colorlab* specification.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
numeric or tuple
Normalised *Munsell* *Colorlab* specification.
Examples
--------
>>> normalize_munsell_specification((0.0, 2.0, 4.0, 6))
(10, 2.0, 4.0, 7)
"""
if is_grey_munsell_colour(specification):
return specification
else:
hue, value, chroma, code = specification
if hue == 0:
# 0YR is equivalent to 10R.
hue, code = 10, (code + 1) % 10
return value if chroma == 0 else (hue, value, chroma, code)
[docs]def munsell_colour_to_munsell_specification(munsell_colour):
"""
Convenient definition to retrieve a normalised *Munsell* *Colorlab*
specification from given *Munsell* colour.
Parameters
----------
munsell_colour : unicode
*Munsell* colour.
Returns
-------
numeric or tuple
Normalised *Munsell* *Colorlab* specification.
Examples
--------
>>> munsell_colour_to_munsell_specification('N5.2') # doctest: +ELLIPSIS
5.2...
>>> munsell_colour_to_munsell_specification('0YR 2.0/4.0')
(10, 2.0, 4.0, 7)
"""
return normalize_munsell_specification(
parse_munsell_colour(munsell_colour))
[docs]def munsell_specification_to_munsell_colour(specification,
hue_decimals=1,
value_decimals=1,
chroma_decimals=1):
"""
Converts from *Munsell* *Colorlab* specification to given *Munsell* colour.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
hue_decimals : int, optional
Hue formatting decimals.
value_decimals : int, optional
Value formatting decimals.
chroma_decimals : int, optional
Chroma formatting decimals.
Returns
-------
unicode
*Munsell* colour.
Examples
--------
>>> # Doctests skip for Python 2.x compatibility.
>>> munsell_specification_to_munsell_colour(5.2) # doctest: +SKIP
'N5.2'
>>> # Doctests skip for Python 2.x compatibility.
>>> spc = (10, 2.0, 4.0, 7)
>>> munsell_specification_to_munsell_colour(spc) # doctest: +SKIP
'10.0R 2.0/4.0'
"""
if is_grey_munsell_colour(specification):
return MUNSELL_GRAY_EXTENDED_FORMAT.format(
specification, value_decimals)
else:
hue, value, chroma, code = specification
code_values = MUNSELL_HUE_LETTER_CODES.values()
assert 0 <= hue <= 10, (
'"{0}" specification hue must be in domain [0, 10]!'.format(
specification))
assert 0 <= value <= 10, (
'"{0}" specification value must be in domain [0, 10]!'.format(
specification))
assert 2 <= chroma <= 50, (
'"{0}" specification chroma must be in domain [2, 50]!'.format(
specification))
assert code in code_values, (
'"{0}" specification code must one of "{1}"!'.format(
specification, code_values))
if hue == 0:
hue, code = 10, (code + 1) % 10
if value == 0:
return MUNSELL_GRAY_EXTENDED_FORMAT.format(
specification, value_decimals)
else:
hue_letter = MUNSELL_HUE_LETTER_CODES.first_key_from_value(
code)
return MUNSELL_COLOUR_EXTENDED_FORMAT.format(hue,
hue_decimals,
hue_letter,
value,
value_decimals,
chroma,
chroma_decimals)
[docs]def xyY_from_renotation(specification):
"""
Returns given existing *Munsell* *Colorlab* specification *CIE xyY*
colourspace vector from *Munsell Renotation System* data.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
tuple
*CIE xyY* colourspace vector.
Raises
------
ValueError
If the given specification doesn't exist in *Munsell Renotation System*
data.
Examples
--------
>>> xyY_from_renotation((2.5, 0.2, 2.0, 4)) # doctest: +ELLIPSIS
(0.71..., 1.41..., 0.23...)
"""
specifications = _munsell_specifications()
try:
return MUNSELL_COLOURS_ALL[specifications.index(specification)][1]
except ValueError:
# TODO: Should raise KeyError, need to check the tests.
raise ValueError(
('"{0}" specification does not exists in '
'"Munsell Renotation System" data!').format(specification))
[docs]def is_specification_in_renotation(specification):
"""
Returns if given *Munsell* *Colorlab* specification is in
*Munsell Renotation System* data.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
bool
Is specification in *Munsell Renotation System* data.
Examples
--------
>>> is_specification_in_renotation((2.5, 0.2, 2.0, 4))
True
>>> is_specification_in_renotation((64, 0.2, 2.0, 4))
False
"""
try:
xyY_from_renotation(specification)
return True
except ValueError:
return False
[docs]def bounding_hues_from_renotation(hue, code):
"""
Returns for a given hue the two bounding hues from
*Munsell Renotation System* data.
Parameters
----------
hue : numeric
*Munsell* *Colorlab* specification hue.
code : numeric
*Munsell* *Colorlab* specification code.
Returns
-------
tuple
Bounding hues.
References
----------
.. [7] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellSystemRoutines/BoundingRenotationHues.m. Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> bounding_hues_from_renotation(3.2, 4)
((2.5, 4), (5.0, 4))
"""
if hue % 2.5 == 0:
if hue == 0:
hue_cw = 10
code_cw = (code + 1) % 10
else:
hue_cw = hue
code_cw = code
hue_ccw = hue_cw
code_ccw = code_cw
else:
hue_cw = 2.5 * np.floor(hue / 2.5)
hue_ccw = (hue_cw + 2.5) % 10
if hue_ccw == 0:
hue_ccw = 10
code_ccw = code
if hue_cw == 0:
hue_cw = 10
code_cw = (code + 1) % 10
if code_cw == 0:
code_cw = 10
else:
code_cw = code
code_ccw = code
return (hue_cw, code_cw), (hue_ccw, code_ccw)
[docs]def hue_to_hue_angle(hue, code):
"""
Converts from the *Munsell* *Colorlab* specification hue to hue angle in
degrees.
Parameters
----------
hue : numeric
*Munsell* *Colorlab* specification hue.
code : numeric
*Munsell* *Colorlab* specification code.
Returns
-------
numeric
Hue angle in degrees.
References
----------
.. [8] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/MunsellHueToChromDiagHueAngle.m.
Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> hue_to_hue_angle(3.2, 4)
65.5
"""
single_hue = ((17 - code) % 10 + (hue / 10) - 0.5) % 10
return LinearInterpolator(
(0, 2, 3, 4, 5, 6, 8, 9, 10),
(0, 45, 70, 135, 160, 225, 255, 315, 360))(single_hue)
[docs]def hue_angle_to_hue(hue_angle):
"""
Converts from hue angle in degrees to the *Munsell* *Colorlab*
specification hue.
Parameters
----------
hue_angle : numeric
Hue angle in degrees.
Returns
-------
tuple
(*Munsell* *Colorlab* specification hue, *Munsell* *Colorlab*
specification code).
References
----------
.. [9] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/ChromDiagHueAngleToMunsellHue.m.
Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> hue_angle_to_hue(65.54) # doctest: +ELLIPSIS
(3.2160000..., 4)
"""
single_hue = LinearInterpolator(
(0, 45, 70, 135, 160, 225, 255, 315, 360),
(0, 2, 3, 4, 5, 6, 8, 9, 10))(hue_angle)
if single_hue <= 0.5:
code = 7
elif single_hue <= 1.5:
code = 6
elif single_hue <= 2.5:
code = 5
elif single_hue <= 3.5:
code = 4
elif single_hue <= 4.5:
code = 3
elif single_hue <= 5.5:
code = 2
elif single_hue <= 6.5:
code = 1
elif single_hue <= 7.5:
code = 10
elif single_hue <= 8.5:
code = 9
elif single_hue <= 9.5:
code = 8
else:
code = 7
hue = (10 * (single_hue % 1) + 5) % 10
if hue == 0:
hue = 10
return hue, code
[docs]def hue_to_ASTM_hue(hue, code):
"""
Converts from the *Munsell* *Colorlab* specification hue to *ASTM* hue
number in domain [0, 100].
Parameters
----------
hue : numeric
*Munsell* *Colorlab* specification hue.
code : numeric
*Munsell* *Colorlab* specification code.
Returns
-------
numeric
*ASM* hue number.
References
----------
.. [10] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/MunsellHueToASTMHue.m. Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> hue_to_ASTM_hue(3.2, 4) # doctest: +ELLIPSIS
33.2...
"""
ASTM_hue = 10 * ((7 - code) % 10) + hue
return 100 if ASTM_hue == 0 else ASTM_hue
[docs]def interpolation_method_from_renotation_ovoid(specification):
"""
Returns whether to use linear or radial interpolation when drawing ovoids
through data points in the *Munsell Renotation System* data from given
specification.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
unicode or None ('Linear', 'Radial', None)
Interpolation method.
Notes
-----
- Input *Munsell* *Colorlab* specification value must be an integer in
domain [0, 10].
- Input *Munsell* *Colorlab* specification chroma must be an integer and
a multiple of 2 in domain [2, 50].
References
----------
.. [11] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellSystemRoutines/LinearVsRadialInterpOnRenotationOvoid.m.
Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> spc = (2.5, 5.0, 12.0, 4)
>>> # Doctests skip for Python 2.x compatibility.
>>> interpolation_method_from_renotation_ovoid() # doctest: +SKIP
'Radial'
"""
interpolation_methods = {0: None,
1: 'Linear',
2: 'Radial'}
interpolation_method = 0
if is_grey_munsell_colour(specification):
# No interpolation needed for grey colours.
interpolation_method = 0
else:
hue, value, chroma, code = specification
assert 0 <= value <= 10, (
'"{0}" specification value must be in domain [0, 10]!'.format(
specification))
assert is_integer(value), (
'"{0}" specification value must be an integer!'.format(
specification))
value = round(value)
# Ideal white, no interpolation needed.
if value == 10:
interpolation_method = 0
assert 2 <= chroma <= 50, (
'"{0}" specification chroma must be in domain [2, 50]!'.format(
specification))
assert abs(
2 * (chroma / 2 - round(chroma / 2))) <= INTEGER_THRESHOLD, (
('"{0}" specification chroma must be an integer and '
'multiple of 2!').format(specification))
chroma = 2 * round(chroma / 2)
# Standard Munsell Renotation System hue, no interpolation needed.
if hue % 2.5 == 0:
interpolation_method = 0
ASTM_hue = hue_to_ASTM_hue(hue, code)
if value == 1:
if chroma == 2:
if 15 < ASTM_hue < 30 or 60 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 4:
if 12.5 < ASTM_hue < 27.5 or 57.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 6:
if 55 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 8:
if 67.5 < ASTM_hue < 77.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 10:
if 72.5 < ASTM_hue < 77.5:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 2:
if chroma == 2:
if 15 < ASTM_hue < 27.5 or 77.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 4:
if 12.5 < ASTM_hue < 30 or 62.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 6:
if 7.5 < ASTM_hue < 22.5 or 62.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 8:
if 7.5 < ASTM_hue < 15 or 60 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 10:
if 65 < ASTM_hue < 77.5:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 3:
if chroma == 2:
if 10 < ASTM_hue < 37.5 or 65 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 4:
if 5 < ASTM_hue < 37.5 or 55 < ASTM_hue < 72.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 6 or chroma == 8 or chroma == 10:
if 7.5 < ASTM_hue < 37.5 or 57.5 < ASTM_hue < 82.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 12:
if 7.5 < ASTM_hue < 42.5 or 57.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 4:
if chroma == 2 or chroma == 4:
if 7.5 < ASTM_hue < 42.5 or 57.5 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 6 or chroma == 8:
if 7.5 < ASTM_hue < 40 or 57.5 < ASTM_hue < 82.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 10:
if 7.5 < ASTM_hue < 40 or 57.5 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 5:
if chroma == 2:
if 5 < ASTM_hue < 37.5 or 55 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 4 or chroma == 6 or chroma == 8:
if 2.5 < ASTM_hue < 42.5 or 55 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 10:
if 2.5 < ASTM_hue < 42.5 or 55 < ASTM_hue < 82.5:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 6:
if chroma == 2 or chroma == 4:
if 5 < ASTM_hue < 37.5 or 55 < ASTM_hue < 87.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 6:
if 5 < ASTM_hue < 42.5 or 57.5 < ASTM_hue < 87.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 8 or chroma == 10:
if 5 < ASTM_hue < 42.5 or 60 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 12 or chroma == 14:
if 5 < ASTM_hue < 42.5 or 60 < ASTM_hue < 82.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 16:
if 5 < ASTM_hue < 42.5 or 60 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 7:
if chroma == 2 or chroma == 4 or chroma == 6:
if 5 < ASTM_hue < 42.5 or 60 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 8:
if 5 < ASTM_hue < 42.5 or 60 < ASTM_hue < 82.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 10:
if (30 < ASTM_hue < 42.5 or
5 < ASTM_hue < 25 or
60 < ASTM_hue < 82.5):
interpolation_method = 2
else:
interpolation_method = 1
elif chroma == 12:
if (30 < ASTM_hue < 42.5 or
7.5 < ASTM_hue < 27.5 or
80 < ASTM_hue < 82.5):
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 14:
if (32.5 < ASTM_hue < 40 or
7.5 < ASTM_hue < 15 or
80 < ASTM_hue < 82.5):
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 8:
if (chroma == 2 or
chroma == 4 or
chroma == 6 or
chroma == 8 or
chroma == 10 or
chroma == 12):
if 5 < ASTM_hue < 40 or 60 < ASTM_hue < 85:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 14:
if (32.5 < ASTM_hue < 40 or
5 < ASTM_hue < 15 or
60 < ASTM_hue < 85):
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
elif value == 9:
if chroma == 2 or chroma == 4:
if 5 < ASTM_hue < 40 or 55 < ASTM_hue < 80:
interpolation_method = 2
else:
interpolation_method = 1
elif (chroma == 6 or
chroma == 8 or
chroma == 10 or
chroma == 12 or
chroma == 14):
if 5 < ASTM_hue < 42.5:
interpolation_method = 2
else:
interpolation_method = 1
elif chroma >= 16:
if 35 < ASTM_hue < 42.5:
interpolation_method = 2
else:
interpolation_method = 1
else:
interpolation_method = 1
return interpolation_methods.get(interpolation_method)
[docs]def xy_from_renotation_ovoid(specification):
"""
Converts given *Munsell* *Colorlab* specification to *xy* chromaticity
coordinates on *Munsell Renotation System* ovoid.
The *xy* point will be on the ovoid about the achromatic point,
corresponding to the *Munsell* *Colorlab* specification
value and chroma.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
tuple
*xy* chromaticity coordinates.
Raises
------
ValueError
If an invalid interpolation method is retrieved from internal
computations.
Notes
-----
- Input *Munsell* *Colorlab* specification value must be an integer in
domain [1, 9].
- Input *Munsell* *Colorlab* specification chroma must be an integer and
a multiple of 2 in domain [2, 50].
References
----------
.. [12] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/FindHueOnRenotationOvoid.m. Retrieved
from https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> xy_from_renotation_ovoid((2.5, 5.0, 12.0, 4)) # doctest: +ELLIPSIS
(0.4333..., 0.5602...)
>>> xy_from_renotation_ovoid(8)
(0.31006, 0.31616)
"""
if is_grey_munsell_colour(specification):
return MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES
else:
hue, value, chroma, code = specification
assert 1 <= value <= 9, (
'"{0}" specification value must be in domain [1, 9]!'.format(
specification))
assert is_integer(value), (
'"{0}" specification value must be an integer!'.format(
specification))
value = round(value)
assert 2 <= chroma <= 50, (
'"{0}" specification chroma must be in domain [2, 50]!'.format(
specification))
assert abs(
2 * (chroma / 2 - round(chroma / 2))) <= INTEGER_THRESHOLD, (
('"{0}" specification chroma must be an integer and '
'multiple of 2!').format(specification))
chroma = 2 * round(chroma / 2)
# Checking if renotation data is available without interpolation using
# given threshold.
threshold = 0.001
if (abs(hue) < threshold or
abs(hue - 2.5) < threshold or
abs(hue - 5) < threshold or
abs(hue - 7.5) < threshold or
abs(hue - 10) < threshold):
hue = 2.5 * round(hue / 2.5)
x, y, _Y = xyY_from_renotation((hue, value, chroma, code))
return x, y
hue_cw, hue_ccw = bounding_hues_from_renotation(hue, code)
hue_minus, code_minus = hue_cw
hue_plus, code_plus = hue_ccw
x_grey, y_grey = MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES
specification_minus = (hue_minus, value, chroma, code_minus)
x_minus, y_minus, Y_minus = xyY_from_renotation(
specification_minus)
_z_minus, theta_minus, rho_minus = cartesian_to_cylindrical(
(x_minus - x_grey, y_minus - y_grey, Y_minus))
theta_minus = np.degrees(theta_minus)
specification_plus = (hue_plus, value, chroma, code_plus)
x_plus, y_plus, Y_plus = xyY_from_renotation(specification_plus)
_z_plus, theta_plus, rho_plus = cartesian_to_cylindrical(
(x_plus - x_grey, y_plus - y_grey, Y_plus))
theta_plus = np.degrees(theta_plus)
lower_hue_angle = hue_to_hue_angle(hue_minus, code_minus)
hue_angle = hue_to_hue_angle(hue, code)
upper_hue_angle = hue_to_hue_angle(hue_plus, code_plus)
if theta_minus - theta_plus > 180:
theta_plus += +360
if lower_hue_angle == 0:
lower_hue_angle = 360
if lower_hue_angle > upper_hue_angle:
if lower_hue_angle > hue_angle:
lower_hue_angle -= 360
else:
lower_hue_angle -= 360
hue_angle -= 360
interpolation_method = interpolation_method_from_renotation_ovoid(
specification).lower()
if interpolation_method == 'linear':
x = LinearInterpolator((lower_hue_angle, upper_hue_angle),
(x_minus, x_plus))(hue_angle)
y = LinearInterpolator((lower_hue_angle, upper_hue_angle),
(y_minus, y_plus))(hue_angle)
elif interpolation_method == 'radial':
theta = LinearInterpolator((lower_hue_angle, upper_hue_angle),
(theta_minus, theta_plus))(hue_angle)
rho = LinearInterpolator((lower_hue_angle, upper_hue_angle),
(rho_minus, rho_plus))(hue_angle)
x = rho * np.cos(np.radians(theta)) + x_grey
y = rho * np.sin(np.radians(theta)) + y_grey
else:
raise ValueError(
'Invalid interpolation method: "{0}"'.format(
interpolation_method))
return x, y
[docs]def LCHab_to_munsell_specification(LCHab):
"""
Converts from *CIE LCHab* colourspace to approximate *Munsell* *Colorlab*
specification.
Parameters
----------
LCHab : array_like, (3,)
*CIE LCHab* colourspace array.
Returns
-------
tuple
*Munsell* *Colorlab* specification.
Notes
-----
- Input :math:`L^*` is in domain [0, 100].
References
----------
.. [13] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
GeneralRoutines/CIELABtoApproxMunsellSpec.m. Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> LCHab = np.array([100, 17.50664796, 244.93046842])
>>> LCHab_to_munsell_specification(LCHab) # doctest: +ELLIPSIS
(8.0362412..., 10.0, 3.5013295..., 1)
"""
L, C, Hab = np.ravel(LCHab)
if Hab == 0:
code = 8
elif Hab <= 36:
code = 7
elif Hab <= 72:
code = 6
elif Hab <= 108:
code = 5
elif Hab <= 144:
code = 4
elif Hab <= 180:
code = 3
elif Hab <= 216:
code = 2
elif Hab <= 252:
code = 1
elif Hab <= 288:
code = 10
elif Hab <= 324:
code = 9
else:
code = 8
hue = LinearInterpolator((0, 36), (0, 10))(Hab % 36)
if hue == 0:
hue = 10
value = L / 10
chroma = C / 5
return hue, value, chroma, code
[docs]def maximum_chroma_from_renotation(hue, value, code):
"""
Returns the maximum *Munsell* chroma from *Munsell Renotation System* data
using given *Munsell* *Colorlab* specification hue, *Munsell* *Colorlab*
specification value and *Munsell* *Colorlab* specification code.
Parameters
----------
hue : numeric
*Munsell* *Colorlab* specification hue.
value : numeric
*Munsell* value code.
code : numeric
*Munsell* *Colorlab* specification code.
Returns
-------
numeric
Maximum chroma.
References
----------
.. [14] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/MaxChromaForExtrapolatedRenotation.m.
Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> maximum_chroma_from_renotation(2.5, 5, 5)
14.0
"""
# Ideal white, no chroma.
if value >= 9.99:
return 0
assert 1 <= value <= 10, (
'"{0}" value must be in domain [1, 10]!'.format(value))
if value % 1 == 0:
value_minus = value
value_plus = value
else:
value_minus = np.floor(value)
value_plus = value_minus + 1
hue_cw, hue_ccw = bounding_hues_from_renotation(hue, code)
hue_cw, code_cw = hue_cw
hue_ccw, code_ccw = hue_ccw
maximum_chromas = _munsell_maximum_chromas_from_renotation()
spc_for_indexes = [chroma[0] for chroma in maximum_chromas]
ma_limit_mcw = maximum_chromas[
spc_for_indexes.index((hue_cw, value_minus, code_cw))][1]
ma_limit_mccw = maximum_chromas[
spc_for_indexes.index((hue_ccw, value_minus, code_ccw))][1]
if value_plus <= 9:
ma_limit_pcw = maximum_chromas[
spc_for_indexes.index((hue_cw, value_plus, code_cw))][1]
ma_limit_pccw = maximum_chromas[
spc_for_indexes.index((hue_ccw, value_plus, code_ccw))][1]
max_chroma = min(ma_limit_mcw,
ma_limit_mccw,
ma_limit_pcw,
ma_limit_pccw)
else:
L = luminance_ASTMD153508(value)
L9 = luminance_ASTMD153508(9)
L10 = luminance_ASTMD153508(10)
max_chroma = min(LinearInterpolator((L9, L10), (ma_limit_mcw, 0))(L),
LinearInterpolator((L9, L10), (ma_limit_mccw, 0))(
L))
return max_chroma
[docs]def munsell_specification_to_xy(specification):
"""
Converts given *Munsell* *Colorlab* specification to *xy* chromaticity
coordinates by interpolating over *Munsell Renotation System* data.
Parameters
----------
specification : numeric or tuple
*Munsell* *Colorlab* specification.
Returns
-------
tuple
*xy* chromaticity coordinates.
Notes
-----
- Input *Munsell* *Colorlab* specification value must be an integer in
domain [0, 10].
- Output *xy* chromaticity coordinates are in domain [0, 1].
References
----------
.. [15] Centore, P. (2014). MunsellAndKubelkaMunkToolboxApr2014 -
MunsellRenotationRoutines/MunsellToxyForIntegerMunsellValue.m.
Retrieved from
https://github.com/colour-science/MunsellAndKubelkaMunkToolbox
Examples
--------
>>> # Doctests ellipsis for Python 2.x compatibility.
>>> munsell_specification_to_xy((2.1, 8.0, 17.9, 4)) # doctest: +ELLIPSIS
(0.440063..., 0.552242...)
>>> munsell_specification_to_xy(8) # doctest: +ELLIPSIS
(0.31006..., 0.31616...)
"""
if is_grey_munsell_colour(specification):
return MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES
else:
hue, value, chroma, code = specification
assert 0 <= value <= 10, (
'"{0}" specification value must be in domain [0, 10]!'.format(
specification))
assert is_integer(value), (
'"{0}" specification value must be an integer!'.format(
specification))
value = round(value)
if chroma % 2 == 0:
chroma_minus = chroma_plus = chroma
else:
chroma_minus = 2 * np.floor(chroma / 2)
chroma_plus = chroma_minus + 2
if chroma_minus == 0:
# Smallest chroma ovoid collapses to illuminant chromaticity
# coordinates.
x_minus, y_minus = (
MUNSELL_DEFAULT_ILLUMINANT_CHROMATICITY_COORDINATES)
else:
x_minus, y_minus = xy_from_renotation_ovoid(
(hue, value, chroma_minus, code))
x_plus, y_plus = xy_from_renotation_ovoid(
(hue, value, chroma_plus, code))
if chroma_minus == chroma_plus:
x = x_minus
y = y_minus
else:
x = LinearInterpolator((chroma_minus, chroma_plus),
(x_minus, x_plus))(chroma)
y = LinearInterpolator((chroma_minus, chroma_plus),
(y_minus, y_plus))(chroma)
return x, y
Colour 0.3