def test_edge_case_behaviour():
""" Check edge case behavior to detect upstream changes
For edge cases where a pixel has the same distance to several regions,
lexicographical order seems to determine which region gets to expand
into this pixel given the current upstream behaviour in
scipy.ndimage.distance_map_edt.
As a result, we expect different results when transposing the array.
If this test fails, something has changed upstream.
"""
expanded = expand_labels(SAMPLE_EDGECASE_BEHAVIOUR, 1)
expanded_transpose = expand_labels(SAMPLE_EDGECASE_BEHAVIOUR.T, 1)
assert not np.all(expanded == expanded_transpose.T)
def test_binary_blobs(ndim, distance):
"""Check some invariants with label expansion.
- New labels array should exactly contain the original labels array.
- Distance to old labels array within new labels should never exceed input
distance.
- Distance beyond the expanded labels should always exceed the input
distance.
"""
img = data.binary_blobs(length=64, blob_size_fraction=0.05, n_dim=ndim)
labels = measure.label(img)
expanded = expand_labels(labels, distance=distance)
original_mask = labels != 0
assert_array_equal(labels[original_mask], expanded[original_mask])
expanded_only_mask = (expanded - labels).astype(bool)
distance_map = ndi.distance_transform_edt(~original_mask)
expanded_distances = distance_map[expanded_only_mask]
if expanded_distances.size > 0:
assert np.all(expanded_distances <= distance)
beyond_expanded_distances = distance_map[~expanded.astype(bool)]
if beyond_expanded_distances.size > 0:
assert np.all(beyond_expanded_distances > distance)
def test_expand_labels(input_array, expected_output, expand_distance):
expanded = expand_labels(input_array, expand_distance)
assert_array_equal(expanded, expected_output)