Source code for colour.recovery.smits1999

# -*- coding: utf-8 -*-
"""
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
"""

import numpy as np

from colour.colorimetry import CCS_ILLUMINANTS
from colour.models import (XYZ_to_RGB, normalised_primary_matrix,
                           RGB_COLOURSPACE_sRGB)
from colour.recovery import SDS_SMITS1999
from colour.utilities import to_domain_1

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2021 - 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__ = [
    'PRIMARIES_SMITS1999', 'CCS_WHITEPOINT_SMITS1999',
    'MATRIX_XYZ_TO_RGB_SMITS1999', 'XYZ_to_RGB_Smits1999',
    'RGB_to_sd_Smits1999'
]

PRIMARIES_SMITS1999 = RGB_COLOURSPACE_sRGB.primaries
"""
Current *Smits (1999)* method implementation colourspace primaries.

PRIMARIES_SMITS1999 : ndarray, (3, 2)
"""

CCS_WHITEPOINT_SMITS1999 = (
    CCS_ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['E'])
"""
Current *Smits (1999)* method implementation colourspace whitepoint.

CCS_WHITEPOINT_SMITS1999 : ndarray
"""

MATRIX_XYZ_TO_RGB_SMITS1999 = np.linalg.inv(
    normalised_primary_matrix(PRIMARIES_SMITS1999, CCS_WHITEPOINT_SMITS1999))
"""
Current *Smits (1999)* method implementation *RGB* colourspace to
*CIE XYZ* tristimulus values matrix.

MATRIX_XYZ_TO_RGB_SMITS1999 : 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,
        CCS_WHITEPOINT_SMITS1999,
        CCS_WHITEPOINT_SMITS1999,
        MATRIX_XYZ_TO_RGB_SMITS1999,
    )


[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.colorimetry import ( ... MSDS_CMFS_STANDARD_OBSERVER, SDS_ILLUMINANTS, ... SpectralShape, 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_STANDARD_OBSERVER['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...]], interpolator=LinearInterpolator, interpolator_kwargs={}, extrapolator=Extrapolator, extrapolator_kwargs={...}) >>> sd_to_XYZ_integration(sd, cmfs, illuminant) / 100 # doctest: +ELLIPSIS array([ 0.1894770..., 0.1126470..., 0.0474420...]) """ white_sd = SDS_SMITS1999['white'].copy() cyan_sd = SDS_SMITS1999['cyan'].copy() magenta_sd = SDS_SMITS1999['magenta'].copy() yellow_sd = SDS_SMITS1999['yellow'].copy() red_sd = SDS_SMITS1999['red'].copy() green_sd = SDS_SMITS1999['green'].copy() blue_sd = SDS_SMITS1999['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