Source code for colour.difference.din99

# -*- coding: utf-8 -*-
"""
:math:`\\Delta E_{99}` DIN99 - Colour Difference Formula
========================================================

Defines the :math:`\\Delta E_{99}` *DIN99* colour difference formula:

-   :func:`colour.difference.delta_E_DIN99`

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
"""

from colour.algebra import euclidean_distance
from colour.models import Lab_to_DIN99
from colour.utilities import get_domain_range_scale

__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__ = ['delta_E_DIN99']


[docs]def delta_E_DIN99(Lab_1, Lab_2, textiles=False): """ Returns the difference :math:`\\Delta E_{DIN99}` between two given *CIE L\\*a\\*b\\** colourspace arrays using *DIN99* formula. Parameters ---------- Lab_1 : array_like *CIE L\\*a\\*b\\** colourspace array 1. Lab_2 : array_like *CIE L\\*a\\*b\\** colourspace array 2. textiles : bool, optional Textiles application specific parametric factors, :math:`k_E=2,\\ k_{CH}=0.5` weights are used instead of :math:`k_E=1,\\ k_{CH}=1`. Returns ------- numeric or ndarray Colour difference :math:`\\Delta E_{DIN99}`. Notes ----- +------------+-----------------------+-------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+===================+ | ``Lab_1`` | ``L_1`` : [0, 100] | ``L_1`` : [0, 1] | | | | | | | ``a_1`` : [-100, 100] | ``a_1`` : [-1, 1] | | | | | | | ``b_1`` : [-100, 100] | ``b_1`` : [-1, 1] | +------------+-----------------------+-------------------+ | ``Lab_2`` | ``L_2`` : [0, 100] | ``L_2`` : [0, 1] | | | | | | | ``a_2`` : [-100, 100] | ``a_2`` : [-1, 1] | | | | | | | ``b_2`` : [-100, 100] | ``b_2`` : [-1, 1] | +------------+-----------------------+-------------------+ References ---------- :cite:`ASTMInternational2007` Examples -------- >>> import numpy as np >>> Lab_1 = np.array([60.2574, -34.0099, 36.2677]) >>> Lab_2 = np.array([60.4626, -34.1751, 39.4387]) >>> delta_E_DIN99(Lab_1, Lab_2) # doctest: +ELLIPSIS 1.1772166... """ k_E = 2 if textiles else 1 k_CH = 0.5 if textiles else 1 factor = 100 if get_domain_range_scale() == '1' else 1 d_E = euclidean_distance( Lab_to_DIN99(Lab_1, k_E, k_CH) * factor, Lab_to_DIN99(Lab_2, k_E, k_CH) * factor) return d_E