# -*- coding: utf-8 -*-
"""
Smits (1999) - Reflectance Recovery
===================================
Defines objects for reflectance recovery using *Smits (1999)* method.
See Also
--------
`Smits (1999) - Reflectance Recovery Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/recovery/smits1999.ipynb>`_
References
----------
- :cite:`Smits1999a` : Smits, B. (1999). An RGB-to-Spectrum Conversion for
Reflectances. Journal of Graphics Tools, 4(4), 11-22.
doi:10.1080/10867651.1999.10487511
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.colorimetry import ILLUMINANTS
from colour.models import (XYZ_to_RGB, normalised_primary_matrix,
sRGB_COLOURSPACE)
from colour.recovery import SMITS_1999_SDS
from colour.utilities import to_domain_1
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-developers@colour-science.org'
__status__ = 'Production'
__all__ = [
'SMITS1999_PRIMARIES', 'SMITS1999_WHITEPOINT',
'SMITS1999_XYZ_TO_RGB_MATRIX', 'XYZ_to_RGB_Smits1999',
'RGB_to_sd_Smits1999'
]
SMITS1999_PRIMARIES = sRGB_COLOURSPACE.primaries
"""
Current *Smits (1999)* method implementation colourspace primaries.
SMITS1999_PRIMARIES : ndarray, (3, 2)
"""
SMITS1999_WHITEPOINT = (
ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['E'])
"""
Current *Smits (1999)* method implementation colourspace whitepoint.
SMITS1999_WHITEPOINT : ndarray
"""
SMITS1999_XYZ_TO_RGB_MATRIX = np.linalg.inv(
normalised_primary_matrix(SMITS1999_PRIMARIES, SMITS1999_WHITEPOINT))
"""
Current *Smits (1999)* method implementation *RGB* colourspace to
*CIE XYZ* tristimulus values matrix.
SMITS1999_XYZ_TO_RGB_MATRIX : array_like, (3, 3)
"""
def XYZ_to_RGB_Smits1999(XYZ):
"""
Convenient object to convert from *CIE XYZ* tristimulus values to *RGB*
colourspace in conditions required by the current *Smits (1999)* method
implementation.
Parameters
----------
XYZ : array_like
*CIE XYZ* tristimulus values.
Returns
-------
ndarray
*RGB* colour array.
Examples
--------
>>> XYZ = np.array([0.21781186, 0.12541048, 0.04697113])
>>> XYZ_to_RGB_Smits1999(XYZ) # doctest: +ELLIPSIS
array([ 0.4063959..., 0.0275289..., 0.0398219...])
"""
return XYZ_to_RGB(
XYZ,
SMITS1999_WHITEPOINT,
SMITS1999_WHITEPOINT,
SMITS1999_XYZ_TO_RGB_MATRIX,
cctf_encoding=None)
[docs]def RGB_to_sd_Smits1999(RGB):
"""
Recovers the spectral distribution of given *RGB* colourspace array using
*Smits (1999)* method.
Parameters
----------
RGB : array_like, (3,)
*RGB* colourspace array to recover the spectral distribution from.
Returns
-------
SpectralDistribution
Recovered spectral distribution.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``RGB`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Smits1999a`
Examples
--------
>>> from colour.utilities import numpy_print_options
>>> RGB = np.array([0.40639599, 0.02752894, 0.03982193])
>>> with numpy_print_options(suppress=True):
... RGB_to_sd_Smits1999(RGB) # doctest: +ELLIPSIS
SpectralDistribution([[ 380. , 0.0769192...],
[ 417.7778 , 0.0587004...],
[ 455.5556 , 0.0394319...],
[ 493.3333 , 0.0302497...],
[ 531.1111 , 0.0275069...],
[ 568.8889 , 0.0280864...],
[ 606.6667 , 0.3429898...],
[ 644.4444 , 0.4118579...],
[ 682.2222 , 0.4118579...],
[ 720. , 0.4118075...]],
interpolator=LinearInterpolator,
interpolator_args={},
extrapolator=Extrapolator,
extrapolator_args={...})
"""
white_sd = SMITS_1999_SDS['white'].copy()
cyan_sd = SMITS_1999_SDS['cyan'].copy()
magenta_sd = SMITS_1999_SDS['magenta'].copy()
yellow_sd = SMITS_1999_SDS['yellow'].copy()
red_sd = SMITS_1999_SDS['red'].copy()
green_sd = SMITS_1999_SDS['green'].copy()
blue_sd = SMITS_1999_SDS['blue'].copy()
R, G, B = to_domain_1(RGB)
sd = white_sd.copy() * 0
sd.name = 'Smits (1999) - {0}'.format(RGB)
if R <= G and R <= B:
sd += white_sd * R
if G <= B:
sd += cyan_sd * (G - R)
sd += blue_sd * (B - G)
else:
sd += cyan_sd * (B - R)
sd += green_sd * (G - B)
elif G <= R and G <= B:
sd += white_sd * G
if R <= B:
sd += magenta_sd * (R - G)
sd += blue_sd * (B - R)
else:
sd += magenta_sd * (B - G)
sd += red_sd * (R - B)
else:
sd += white_sd * B
if R <= G:
sd += yellow_sd * (R - B)
sd += green_sd * (G - R)
else:
sd += yellow_sd * (G - B)
sd += red_sd * (R - G)
return sd