180 lines
5.4 KiB
Python
180 lines
5.4 KiB
Python
"""Test for correctness of color distance functions"""
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from os.path import abspath, dirname, join as pjoin
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import numpy as np
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from skimage._shared.testing import (
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assert_allclose, assert_equal, assert_almost_equal, fetch
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)
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from skimage.color.delta_e import (
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deltaE_cie76, deltaE_ciede94, deltaE_ciede2000, deltaE_cmc
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)
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def test_ciede2000_dE():
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data = load_ciede2000_data()
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N = len(data)
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lab1 = np.zeros((N, 3))
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lab1[:, 0] = data['L1']
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lab1[:, 1] = data['a1']
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lab1[:, 2] = data['b1']
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lab2 = np.zeros((N, 3))
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lab2[:, 0] = data['L2']
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lab2[:, 1] = data['a2']
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lab2[:, 2] = data['b2']
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dE2 = deltaE_ciede2000(lab1, lab2)
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assert_allclose(dE2, data['dE'], rtol=1.e-4)
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def load_ciede2000_data():
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dtype = [('pair', int),
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('1', int),
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('L1', float),
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('a1', float),
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('b1', float),
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('a1_prime', float),
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('C1_prime', float),
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('h1_prime', float),
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('hbar_prime', float),
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('G', float),
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('T', float),
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('SL', float),
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('SC', float),
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('SH', float),
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('RT', float),
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('dE', float),
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('2', int),
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('L2', float),
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('a2', float),
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('b2', float),
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('a2_prime', float),
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('C2_prime', float),
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('h2_prime', float),
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]
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# note: ciede_test_data.txt contains several intermediate quantities
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path = fetch('color/tests/ciede2000_test_data.txt')
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return np.loadtxt(path, dtype=dtype)
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def test_cie76():
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data = load_ciede2000_data()
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N = len(data)
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lab1 = np.zeros((N, 3))
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lab1[:, 0] = data['L1']
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lab1[:, 1] = data['a1']
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lab1[:, 2] = data['b1']
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lab2 = np.zeros((N, 3))
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lab2[:, 0] = data['L2']
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lab2[:, 1] = data['a2']
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lab2[:, 2] = data['b2']
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dE2 = deltaE_cie76(lab1, lab2)
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oracle = np.array([
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4.00106328, 6.31415011, 9.1776999, 2.06270077, 2.36957073,
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2.91529271, 2.23606798, 2.23606798, 4.98000036, 4.9800004,
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4.98000044, 4.98000049, 4.98000036, 4.9800004, 4.98000044,
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3.53553391, 36.86800781, 31.91002977, 30.25309901, 27.40894015,
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0.89242934, 0.7972, 0.8583065, 0.82982507, 3.1819238,
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2.21334297, 1.53890382, 4.60630929, 6.58467989, 3.88641412,
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1.50514845, 2.3237848, 0.94413208, 1.31910843
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])
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assert_allclose(dE2, oracle, rtol=1.e-8)
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def test_ciede94():
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data = load_ciede2000_data()
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N = len(data)
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lab1 = np.zeros((N, 3))
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lab1[:, 0] = data['L1']
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lab1[:, 1] = data['a1']
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lab1[:, 2] = data['b1']
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lab2 = np.zeros((N, 3))
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lab2[:, 0] = data['L2']
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lab2[:, 1] = data['a2']
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lab2[:, 2] = data['b2']
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dE2 = deltaE_ciede94(lab1, lab2)
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oracle = np.array([
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1.39503887, 1.93410055, 2.45433566, 0.68449187, 0.6695627,
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0.69194527, 2.23606798, 2.03163832, 4.80069441, 4.80069445,
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4.80069449, 4.80069453, 4.80069441, 4.80069445, 4.80069449,
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3.40774352, 34.6891632, 29.44137328, 27.91408781, 24.93766082,
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0.82213163, 0.71658427, 0.8048753, 0.75284394, 1.39099471,
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1.24808929, 1.29795787, 1.82045088, 2.55613309, 1.42491303,
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1.41945261, 2.3225685, 0.93853308, 1.30654464
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])
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assert_allclose(dE2, oracle, rtol=1.e-8)
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def test_cmc():
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data = load_ciede2000_data()
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N = len(data)
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lab1 = np.zeros((N, 3))
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lab1[:, 0] = data['L1']
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lab1[:, 1] = data['a1']
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lab1[:, 2] = data['b1']
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lab2 = np.zeros((N, 3))
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lab2[:, 0] = data['L2']
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lab2[:, 1] = data['a2']
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lab2[:, 2] = data['b2']
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dE2 = deltaE_cmc(lab1, lab2)
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oracle = np.array([
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1.73873611, 2.49660844, 3.30494501, 0.85735576, 0.88332927,
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0.97822692, 3.50480874, 2.87930032, 6.5783807, 6.57838075,
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6.5783808, 6.57838086, 6.67492321, 6.67492326, 6.67492331,
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4.66852997, 42.10875485, 39.45889064, 38.36005919, 33.93663807,
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1.14400168, 1.00600419, 1.11302547, 1.05335328, 1.42822951,
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1.2548143, 1.76838061, 2.02583367, 3.08695508, 1.74893533,
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1.90095165, 1.70258148, 1.80317207, 2.44934417
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])
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assert_allclose(dE2, oracle, rtol=1.e-8)
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# Equal or close colors make `delta_e.get_dH2` function to return
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# negative values resulting in NaNs when passed to sqrt (see #1908
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# issue on Github):
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lab1 = lab2
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expected = np.zeros_like(oracle)
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assert_almost_equal(deltaE_cmc(lab1, lab2), expected, decimal=6)
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lab2[0, 0] += np.finfo(float).eps
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assert_almost_equal(deltaE_cmc(lab1, lab2), expected, decimal=6)
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# Single item case:
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lab1 = lab2 = np.array([0., 1.59607713, 0.87755709])
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assert_equal(deltaE_cmc(lab1, lab2), 0)
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lab2[0] += np.finfo(float).eps
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assert_equal(deltaE_cmc(lab1, lab2), 0)
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def test_single_color_cie76():
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lab1 = (0.5, 0.5, 0.5)
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lab2 = (0.4, 0.4, 0.4)
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deltaE_cie76(lab1, lab2)
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def test_single_color_ciede94():
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lab1 = (0.5, 0.5, 0.5)
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lab2 = (0.4, 0.4, 0.4)
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deltaE_ciede94(lab1, lab2)
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def test_single_color_ciede2000():
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lab1 = (0.5, 0.5, 0.5)
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lab2 = (0.4, 0.4, 0.4)
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deltaE_ciede2000(lab1, lab2)
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def test_single_color_cmc():
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lab1 = (0.5, 0.5, 0.5)
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lab2 = (0.4, 0.4, 0.4)
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deltaE_cmc(lab1, lab2)
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