from numpy.testing import assert_equal, assert_almost_equal
import numpy as np

from skimage.measure import (moments, moments_central, moments_normalized,
                             moments_hu)


def test_moments():
    image = np.zeros((20, 20), dtype=np.double)
    image[14, 14] = 1
    image[15, 15] = 1
    image[14, 15] = 0.5
    image[15, 14] = 0.5
    m = moments(image)
    assert_equal(m[0, 0], 3)
    assert_almost_equal(m[0, 1] / m[0, 0], 14.5)
    assert_almost_equal(m[1, 0] / m[0, 0], 14.5)


def test_moments_central():
    image = np.zeros((20, 20), dtype=np.double)
    image[14, 14] = 1
    image[15, 15] = 1
    image[14, 15] = 0.5
    image[15, 14] = 0.5
    mu = moments_central(image, 14.5, 14.5)

    # shift image by dx=2, dy=2
    image2 = np.zeros((20, 20), dtype=np.double)
    image2[16, 16] = 1
    image2[17, 17] = 1
    image2[16, 17] = 0.5
    image2[17, 16] = 0.5
    mu2 = moments_central(image2, 14.5 + 2, 14.5 + 2)
    # central moments must be translation invariant
    assert_equal(mu, mu2)


def test_moments_normalized():
    image = np.zeros((20, 20), dtype=np.double)
    image[13:17, 13:17] = 1
    mu = moments_central(image, 14.5, 14.5)
    nu = moments_normalized(mu)
    # shift image by dx=-3, dy=-3 and scale by 0.5
    image2 = np.zeros((20, 20), dtype=np.double)
    image2[11:13, 11:13] = 1
    mu2 = moments_central(image2, 11.5, 11.5)
    nu2 = moments_normalized(mu2)
    # central moments must be translation and scale invariant
    assert_almost_equal(nu, nu2, decimal=1)


def test_moments_hu():
    image = np.zeros((20, 20), dtype=np.double)
    image[13:15, 13:17] = 1
    mu = moments_central(image, 13.5, 14.5)
    nu = moments_normalized(mu)
    hu = moments_hu(nu)
    # shift image by dx=2, dy=3, scale by 0.5 and rotate by 90deg
    image2 = np.zeros((20, 20), dtype=np.double)
    image2[11, 11:13] = 1
    image2 = image2.T
    mu2 = moments_central(image2, 11.5, 11)
    nu2 = moments_normalized(mu2)
    hu2 = moments_hu(nu2)
    # central moments must be translation and scale invariant
    assert_almost_equal(hu, hu2, decimal=1)


if __name__ == "__main__":
    from numpy.testing import run_module_suite
    run_module_suite()

Add test cases for moments functions