GPU support for ndmorph, binary morphological functions (#157)

* GPU support for ndmorph subpackage

* Fix ndmorph default structure for cupy arrays

dask_image/dispatch/_dispatch_ndmorph.py

@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+
+import numpy as np
+import scipy.ndimage
+
+from ._dispatcher import Dispatcher
+
+__all__ = [
+    "dispatch_binary_dilation",
+    "dispatch_binary_erosion",
+    "dispatch_binary_structure",
+]
+
+dispatch_binary_dilation = Dispatcher(name="dispatch_binary_dilation")
+dispatch_binary_erosion = Dispatcher(name="dispatch_binary_erosion")
+dispatch_binary_structure = Dispatcher(name='dispatch_binary_structure')
+
+
+# ================== binary_dilation ==================
+@dispatch_binary_dilation.register(np.ndarray)
+def numpy_binary_dilation(*args, **kwargs):
+    return scipy.ndimage.binary_dilation
+
+
+@dispatch_binary_dilation.register_lazy("cupy")
+def register_cupy_binary_dilation():
+    import cupy
+    import cupyx.scipy.ndimage
+
+    @dispatch_binary_dilation.register(cupy.ndarray)
+    def cupy_binary_dilation(*args, **kwargs):
+        return cupyx.scipy.ndimage.binary_dilation
+
+
+# ================== binary_erosion ==================
+@dispatch_binary_erosion.register(np.ndarray)
+def numpy_binary_erosion(*args, **kwargs):
+    return scipy.ndimage.binary_erosion
+
+
+@dispatch_binary_erosion.register_lazy("cupy")
+def register_cupy_binary_erosion():
+    import cupy
+    import cupyx.scipy.ndimage
+
+    @dispatch_binary_erosion.register(cupy.ndarray)
+    def cupy_binary_erosion(*args, **kwargs):
+        return cupyx.scipy.ndimage.binary_erosion
+
+
+# ================== generate_binary_structure ==================
+@dispatch_binary_structure.register(np.ndarray)
+def numpy_binary_structure(*args, **kwargs):
+    return scipy.ndimage.generate_binary_structure
+
+
+@dispatch_binary_structure.register_lazy("cupy")
+def register_cupy_binary_structure():
+    import cupy
+    import cupyx.scipy.ndimage
+
+    @dispatch_binary_structure.register(cupy.ndarray)
+    def cupy_binary_structure(*args, **kwargs):
+        return cupyx.scipy.ndimage.generate_binary_structure

dask_image/ndmorph/__init__.py

@@ -8,6 +8,16 @@
 
 from . import _utils
 from . import _ops
+from ..dispatch._dispatch_ndmorph import (
+    dispatch_binary_dilation,
+    dispatch_binary_erosion)
+
+__all__ = [
+    "binary_closing",
+    "binary_dilation",
+    "binary_erosion",
+    "binary_opening",
+]
 
 
 @_utils._update_wrapper(scipy.ndimage.binary_closing)
@@ -43,7 +53,7 @@ def binary_dilation(image,
     border_value = _utils._get_border_value(border_value)
 
     result = _ops._binary_op(
-        scipy.ndimage.binary_dilation,
+        dispatch_binary_dilation(image),
         image,
         structure=structure,
         iterations=iterations,
@@ -67,7 +77,7 @@ def binary_erosion(image,
     border_value = _utils._get_border_value(border_value)
 
     result = _ops._binary_op(
-        scipy.ndimage.binary_erosion,
+        dispatch_binary_erosion(image),
         image,
         structure=structure,
         iterations=iterations,

dask_image/ndmorph/_utils.py

@@ -8,6 +8,7 @@
 
 import dask.array
 
+from ..dispatch._dispatch_ndmorph import dispatch_binary_structure
 from ..ndfilters._utils import (
     _update_wrapper,
     _get_depth_boundary,
@@ -24,8 +25,9 @@
 def _get_structure(image, structure):
     # Create square connectivity as default
     if structure is None:
-        structure = scipy.ndimage.generate_binary_structure(image.ndim, 1)
-    elif isinstance(structure, (numpy.ndarray, dask.array.Array)):
+        generate_binary_structure = dispatch_binary_structure(image)
+        structure = generate_binary_structure(image.ndim, 1)
+    elif hasattr(structure, 'ndim'):
         if structure.ndim != image.ndim:
             raise RuntimeError(
                 "`structure` must have the same rank as `image`."

tests/test_dask_image/test_ndmorph/test_cupy_ndmorph.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import dask.array as da
+import numpy as np
+import pytest
+
+from dask_image import ndmorph
+
+cupy = pytest.importorskip("cupy", minversion="7.7.0")
+
+
+@pytest.fixture
+def array():
+    s = (10, 10)
+    a = da.from_array(cupy.arange(int(np.prod(s)),
+                      dtype=cupy.float32).reshape(s), chunks=5)
+    return a
+
+
+@pytest.mark.cupy
+@pytest.mark.parametrize("func", [
+    ndmorph.binary_closing,
+    ndmorph.binary_dilation,
+    ndmorph.binary_erosion,
+    ndmorph.binary_opening,
+])
+def test_cupy_ndmorph(array, func):
+    """Test convolve & correlate filters with cupy input arrays."""
+    result = func(array)
+    result.compute()