Source code for colour.models.din99

# -*- coding: utf-8 -*-
"""
DIN99 Colourspace
=================

Defines the *DIN99* colourspace transformations:

-   :func:`colour.Lab_to_DIN99`
-   :func:`colour.DIN99_to_Lab`

References
----------
-   :cite:`ASTMInternational2007` : ASTM International. (2007). ASTM D2244-07 -
    Standard Practice for Calculation of Color Tolerances and Color Differences
    from Instrumentally Measured Color Coordinates: Vol. i (pp. 1-10).
    doi:10.1520/D2244-16
"""

import numpy as np

from colour.algebra import spow
from colour.utilities import from_range_100, tsplit, tstack, to_domain_100

__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__ = ['Lab_to_DIN99', 'DIN99_to_Lab']


[docs]def Lab_to_DIN99(Lab, k_E=1, k_CH=1): """ Converts from *CIE L\\*a\\*b\\** colourspace to *DIN99* colourspace. Parameters ---------- Lab : array_like *CIE L\\*a\\*b\\** colourspace array. k_E : numeric, optional Parametric factor :math:`K_E` used to compensate for texture and other specimen presentation effects. k_CH : numeric, optional Parametric factor :math:`K_{CH}` used to compensate for texture and other specimen presentation effects. Returns ------- ndarray *DIN99* colourspace array. Notes ----- +------------+------------------------+--------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+========================+====================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +------------+------------------------+--------------------+ +------------+------------------------+--------------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+========================+====================+ | ``Lab_99`` | ``L_99`` : [0, 100] | ``L_99`` : [0, 1] | | | | | | | ``a_99`` : [-100, 100] | ``a_99`` : [-1, 1] | | | | | | | ``b_99`` : [-100, 100] | ``b_99`` : [-1, 1] | +------------+------------------------+--------------------+ References ---------- :cite:`ASTMInternational2007` Examples -------- >>> import numpy as np >>> Lab = np.array([41.52787529, 52.63858304, 26.92317922]) >>> Lab_to_DIN99(Lab) # doctest: +ELLIPSIS array([ 53.2282198..., 28.4163465..., 3.8983955...]) """ L, a, b = tsplit(to_domain_100(Lab)) cos_16 = np.cos(np.radians(16)) sin_16 = np.sin(np.radians(16)) e = cos_16 * a + sin_16 * b f = 0.7 * (-sin_16 * a + cos_16 * b) G = spow(e ** 2 + f ** 2, 0.5) h_ef = np.arctan2(f, e) C_99 = (np.log(1 + 0.045 * G)) / (0.045 * k_CH * k_E) # Hue angle is unused currently. # h_99 = np.degrees(h_ef) a_99 = C_99 * np.cos(h_ef) b_99 = C_99 * np.sin(h_ef) L_99 = 105.509 * (np.log(1 + 0.0158 * L)) * k_E Lab_99 = tstack([L_99, a_99, b_99]) return from_range_100(Lab_99)
[docs]def DIN99_to_Lab(Lab_99, k_E=1, k_CH=1): """ Converts from *DIN99* colourspace to *CIE L\\*a\\*b\\** colourspace. Parameters ---------- Lab_99 : array_like *DIN99* colourspace array. k_E : numeric, optional Parametric factor :math:`K_E` used to compensate for texture and other specimen presentation effects. k_CH : numeric, optional Parametric factor :math:`K_{CH}` used to compensate for texture and other specimen presentation effects. Returns ------- ndarray *CIE L\\*a\\*b\\** colourspace array. Notes ----- +------------+------------------------+--------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+========================+====================+ | ``Lab_99`` | ``L_99`` : [0, 100] | ``L_99`` : [0, 1] | | | | | | | ``a_99`` : [-100, 100] | ``a_99`` : [-1, 1] | | | | | | | ``b_99`` : [-100, 100] | ``b_99`` : [-1, 1] | +------------+------------------------+--------------------+ +------------+------------------------+--------------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+========================+====================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +------------+------------------------+--------------------+ References ---------- :cite:`ASTMInternational2007` Examples -------- >>> import numpy as np >>> Lab_99 = np.array([53.22821988, 28.41634656, 3.89839552]) >>> DIN99_to_Lab(Lab_99) # doctest: +ELLIPSIS array([ 41.5278752..., 52.6385830..., 26.9231792...]) """ L_99, a_99, b_99 = tsplit(to_domain_100(Lab_99)) cos_16 = np.cos(np.radians(16)) sin_16 = np.sin(np.radians(16)) h_99 = np.arctan2(b_99, a_99) C_99 = np.sqrt(a_99 ** 2 + b_99 ** 2) G = (np.exp(0.045 * C_99 * k_CH * k_E) - 1) / 0.045 e = G * np.cos(h_99) f = G * np.sin(h_99) a = e * cos_16 - (f / 0.7) * sin_16 b = e * sin_16 + (f / 0.7) * cos_16 L = (np.exp(L_99 * k_E / 105.509) - 1) / 0.0158 Lab = tstack([L, a, b]) return from_range_100(Lab)