Fix and test 0-end bug in crop

skimage/util/arraypad.py

@@ -1530,7 +1530,7 @@ def crop(ar, crop_width, copy=False, order='K'):
     """
     ar = np.array(ar, copy=False)
     crops = _validate_lengths(ar, crop_width)
-    slices = tuple([slice(a, -b) for a, b in crops])
+    slices = [slice(a, ar.shape[i] - b) for i, (a, b) in enumerate(crops)]
     if copy:
         cropped = np.copy(ar[slices], order=order)
     else:

skimage/util/tests/test_arraypad.py

@@ -1081,5 +1081,11 @@ def test_copy_crop():
     assert np.may_share_memory(arr, out1)
 
 
+def test_zero_crop():
+    arr = np.arange(45).reshape(9, 5)
+    out = crop(arr, 0)
+    assert out.shape == (9, 5)
+
+
 if __name__ == "__main__":
     np.testing.run_module_suite()