Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/skimage/morphology/tests/test_util.py

@@ -0,0 +1,127 @@
+"""Tests for `_util`."""
+
+
+import pytest
+import numpy as np
+from numpy.testing import assert_array_equal
+
+from skimage.morphology import _util
+
+
+@pytest.mark.parametrize("image_shape", [
+    (111,), (33, 44), (22, 55, 11), (6, 5, 4, 3)
+])
+@pytest.mark.parametrize("order", ["C", "F"])
+def test_offsets_to_raveled_neighbors_highest_connectivity(image_shape, order):
+    """
+    Check scenarios where selem is always of the highest connectivity
+    and all dimensions are > 2.
+    """
+    selem = np.ones((3,) * len(image_shape), dtype=bool)
+    center = (1,) * len(image_shape)
+    offsets = _util._offsets_to_raveled_neighbors(
+        image_shape, selem, center, order
+    )
+
+    # Assert only neighbors are present, center was removed
+    assert len(offsets) == selem.sum() - 1
+    assert 0 not in offsets
+    # Assert uniqueness
+    assert len(set(offsets)) == offsets.size
+    # offsets form pairs of with same value but different signs
+    # if selem is symmetric around center
+    assert all(-x in offsets for x in offsets)
+
+    # Construct image whose values are the Manhattan distance to its center
+    image_center = tuple(s // 2 for s in image_shape)
+    coords = [
+        np.abs(np.arange(s, dtype=np.intp) - c)
+        for s, c in zip(image_shape, image_center)
+    ]
+    grid = np.meshgrid(*coords, indexing="ij")
+    image = np.sum(grid, axis=0)
+
+    image_raveled = image.ravel(order)
+    image_center_raveled = np.ravel_multi_index(
+        image_center, image_shape, order=order
+    )
+
+    # Sample raveled image around its center
+    samples = []
+    for offset in offsets:
+        index = image_center_raveled + offset
+        samples.append(image_raveled[index])
+
+    # Assert that center with value 0 wasn't selected
+    assert np.min(samples) == 1
+    # Assert that only neighbors where selected
+    # (highest value == connectivity)
+    assert np.max(samples) == len(image_shape)
+    # Assert that nearest neighbors are selected first
+    assert list(sorted(samples)) == samples
+
+
+@pytest.mark.parametrize("image_shape", [
+    (2,), (2, 2), (2, 1, 2), (2, 2, 1, 2), (0, 2, 1, 2)
+])
+@pytest.mark.parametrize("order", ["C", "F"])
+def test_offsets_to_raveled_neighbors_selem_smaller_image(image_shape, order):
+    """
+    Test if a dimension indicated by `image_shape` is smaller than in
+    `selem`.
+    """
+    selem = np.ones((3,) * len(image_shape), dtype=bool)
+    center = (1,) * len(image_shape)
+    offsets = _util._offsets_to_raveled_neighbors(
+        image_shape, selem, center, order
+    )
+
+    # Assert only neighbors are present, center and duplicates (possible
+    # for this scenario) where removed
+    assert len(offsets) <= selem.sum() - 1
+    assert 0 not in offsets
+    # Assert uniqueness
+    assert len(set(offsets)) == offsets.size
+    # offsets form pairs of with same value but different signs
+    # if selem is symmetric around center
+    assert all(-x in offsets for x in offsets)
+
+
+def test_offsets_to_raveled_neighbors_explicit_0():
+    """Check reviewed example."""
+    image_shape = (100, 200, 3)
+    selem = np.ones((3, 3, 3), dtype=bool)
+    center = (1, 1, 1)
+    offsets = _util._offsets_to_raveled_neighbors(
+        image_shape, selem, center
+    )
+
+    desired = np.array([
+          3, -600,    1,   -1,  600,   -3,    4,    2,  603,   -2,   -4,
+        -597,  601, -599, -601, -603,  599,  597,  602, -604,  596, -596,
+        -598, -602,  598,  604
+    ])
+    assert_array_equal(offsets, desired)
+
+
+def test_offsets_to_raveled_neighbors_explicit_1():
+    """Check reviewed example where selem is larger in last dimension."""
+    image_shape = (10, 9, 8, 3)
+    selem = np.ones((3, 3, 3, 4), dtype=bool)
+    center = (1, 1, 1, 1)
+    offsets = _util._offsets_to_raveled_neighbors(
+        image_shape, selem, center
+    )
+
+    desired = np.array([
+          24,    3,    1,   -1,   -3,  -24, -216,  216, -192,  215,   -2,
+         -21,  -23,    2,  -25,  -27,    4,  217,   21,  219,   -4,   23,
+          25, -240,  240,  192,   27, -213, -219,  213, -215, -217, -243,
+         191, -241,  195,  189,  212,   26,    5,   20,   28,   22,  214,
+         243, -237,  -22,  241, -214, -212,  237, -218, -195,  -20,  220,
+        -193, -191,  218, -189,  -28,  -26,  193, -239, -220,  239,  196,
+         221,  242,  236,  238,  194, -244, -188, -238, -211, -196, -194,
+        -190, -236,  -19,  244,   29,  188, -242,  190, -187,  197, -235,
+         245
+    ])
+    assert_array_equal(offsets, desired)