def test_04_max_threshold(self):
"""Test Otsu with a max_threshold"""
numpy.random.seed(0)
#
# There should be three peaks with the otsu
# between the second and third
# With a fixed max threshold, the otsu
# should be between the first two peaks.
x0 = numpy.random.binomial(40, .1, 2000).astype(float) / 40.0
x1 = numpy.random.binomial(40, .5, 2000).astype(float) / 40.0
x2 = numpy.random.binomial(40, .9, 10000).astype(float) / 40.0
x = numpy.concatenate((x0, x1, x2))
self.assertTrue(otsu(x) > .5)
self.assertTrue(otsu(x) < .9)
self.assertTrue(otsu(x, max_threshold=.5) >= .1)
self.assertTrue(otsu(x, max_threshold=.5) <= .5)
def test_05_threshold_of_flat(self):
"""Test Otsu with a threshold and all input values the same
This is a regression test of an apparent bug where the Otsu
of an all-zero image has a threshold of zero even though
the min_threshold was .1
"""
numpy.random.seed(0)
x = numpy.zeros((10, ))
self.assertTrue(otsu(x, min_threshold=.1) >= .1)
def test_02_TwoDistributions(self):
"""Test Otsu of two distributions with no points in between is between the two distributions"""
numpy.random.seed(0)
x0 = numpy.random.uniform(.1, .4, size=1000)
x1 = numpy.random.uniform(.6, 1.0, size=1000)
x = numpy.append(x0, x1)
numpy.random.shuffle(x)
threshold = otsu(x)
self.assertTrue(threshold >= .4)
self.assertTrue(threshold <= .6)
def test_01_TwoValues(self):
"""Test Otsu of two values is between the two"""
x = otsu([.2, .8])
self.assertTrue(x >= .2)
self.assertTrue(x <= .8)