"""
Smits (1999) - Reflectance Recovery
===================================
Defines the objects for reflectance recovery using *Smits (1999)* method.
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 annotations
from colour.colorimetry import CCS_ILLUMINANTS, SpectralDistribution
from colour.hints import ArrayLike, NDArrayFloat
from colour.models import (
RGB_Colourspace,
RGB_COLOURSPACE_sRGB,
XYZ_to_RGB,
)
from colour.recovery import SDS_SMITS1999
from colour.utilities import to_domain_1
__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__ = [
"PRIMARIES_SMITS1999",
"WHITEPOINT_NAME_SMITS1999",
"CCS_WHITEPOINT_SMITS1999",
"RGB_COLOURSPACE_SMITS1999",
"XYZ_to_RGB_Smits1999",
"RGB_to_sd_Smits1999",
]
PRIMARIES_SMITS1999: NDArrayFloat = RGB_COLOURSPACE_sRGB.primaries
"""*Smits (1999)* method implementation colourspace primaries."""
WHITEPOINT_NAME_SMITS1999 = "E"
"""*Smits (1999)* method implementation colourspace whitepoint name."""
CCS_WHITEPOINT_SMITS1999: NDArrayFloat = CCS_ILLUMINANTS[
"CIE 1931 2 Degree Standard Observer"
][WHITEPOINT_NAME_SMITS1999]
"""*Smits (1999)* method implementation colourspace whitepoint."""
RGB_COLOURSPACE_SMITS1999 = RGB_Colourspace(
"Smits 1999",
PRIMARIES_SMITS1999,
CCS_WHITEPOINT_SMITS1999,
WHITEPOINT_NAME_SMITS1999,
)
RGB_COLOURSPACE_sRGB.__doc__ = """
*Smits (1999)* colourspace.
References
----------
:cite:`Smits1999a`,
"""
def XYZ_to_RGB_Smits1999(XYZ: ArrayLike) -> NDArrayFloat:
"""
Convert from *CIE XYZ* tristimulus values to *RGB* colourspace with
conditions required by the current *Smits (1999)* method implementation.
Parameters
----------
XYZ
*CIE XYZ* tristimulus values.
Returns
-------
:class:`numpy.ndarray`
*RGB* colour array.
Examples
--------
>>> import numpy as np
>>> 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, RGB_COLOURSPACE_SMITS1999)
[docs]
def RGB_to_sd_Smits1999(RGB: ArrayLike) -> SpectralDistribution:
"""
Recover the spectral distribution of given *RGB* colourspace array using
*Smits (1999)* method.
Parameters
----------
RGB
*RGB* colourspace array to recover the spectral distribution from.
Returns
-------
:class:`colour.SpectralDistribution`
Recovered spectral distribution.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``RGB`` | [0, 1] | [0, 1] |
+------------+-----------------------+---------------+
References
----------
:cite:`Smits1999a`
Examples
--------
>>> import numpy as np
>>> from colour import MSDS_CMFS, SDS_ILLUMINANTS, SpectralShape
>>> from colour.colorimetry import sd_to_XYZ_integration
>>> from colour.utilities import numpy_print_options
>>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952])
>>> RGB = XYZ_to_RGB_Smits1999(XYZ)
>>> cmfs = (
... MSDS_CMFS["CIE 1931 2 Degree Standard Observer"]
... .copy()
... .align(SpectralShape(360, 780, 10))
... )
>>> illuminant = SDS_ILLUMINANTS["E"].copy().align(cmfs.shape)
>>> sd = RGB_to_sd_Smits1999(RGB)
>>> with numpy_print_options(suppress=True):
... sd # doctest: +ELLIPSIS
...
SpectralDistribution([[ 380. , 0.0787830...],
[ 417.7778 , 0.0622018...],
[ 455.5556 , 0.0446206...],
[ 493.3333 , 0.0352220...],
[ 531.1111 , 0.0324149...],
[ 568.8889 , 0.0330105...],
[ 606.6667 , 0.3207115...],
[ 644.4444 , 0.3836164...],
[ 682.2222 , 0.3836164...],
[ 720. , 0.3835649...]],
LinearInterpolator,
{},
Extrapolator,
{'method': 'Constant', 'left': None, 'right': None})
>>> sd_to_XYZ_integration(sd, cmfs, illuminant) / 100 # doctest: +ELLIPSIS
array([ 0.1894770..., 0.1126470..., 0.0474420...])
"""
sd_white = SDS_SMITS1999["white"].copy()
sd_cyan = SDS_SMITS1999["cyan"].copy()
sd_magenta = SDS_SMITS1999["magenta"].copy()
sd_yellow = SDS_SMITS1999["yellow"].copy()
sd_red = SDS_SMITS1999["red"].copy()
sd_green = SDS_SMITS1999["green"].copy()
sd_blue = SDS_SMITS1999["blue"].copy()
R, G, B = to_domain_1(RGB)
sd = sd_white.copy() * 0
sd.name = f"Smits (1999) - {RGB!r}"
if R <= G and R <= B:
sd += sd_white * R
if G <= B:
sd += sd_cyan * (G - R)
sd += sd_blue * (B - G)
else:
sd += sd_cyan * (B - R)
sd += sd_green * (G - B)
elif G <= R and G <= B:
sd += sd_white * G
if R <= B:
sd += sd_magenta * (R - G)
sd += sd_blue * (B - R)
else:
sd += sd_magenta * (B - G)
sd += sd_red * (R - B)
else:
sd += sd_white * B
if R <= G:
sd += sd_yellow * (R - B)
sd += sd_green * (G - R)
else:
sd += sd_yellow * (G - B)
sd += sd_red * (R - G)
return sd