Allow static background in metadata to be a Dask array

doc/changelog.rst

@@ -41,6 +41,8 @@ Changed
 
 Fixed
 -----
+- Allow static background in EBSD metadata to be a Dask array.
+  (`#413 <https://github.com/pyxem/kikuchipy/pull/413>`_)
 - Set newest supported version of Sphinx to 4.0.2 so that nbsphinx works.
   (`#403 <https://github.com/pyxem/kikuchipy/pull/403>`_)
 

kikuchipy/signals/ebsd.py

@@ -516,29 +516,31 @@ def remove_static_background(
         dtype_out = self.data.dtype.type
 
         # Get background pattern
-        if not isinstance(static_bg, (np.ndarray, da.Array)):
+        if static_bg is None:
             try:
                 md = self.metadata
                 ebsd_node = metadata_nodes("ebsd")
-                static_bg = da.from_array(
-                    md.get_item(ebsd_node + ".static_background"), chunks="auto"
-                )
-            except AttributeError:
-                raise OSError(
-                    "The static background is not a numpy or dask array or could not be"
-                    " read from signal metadata."
+                static_bg_in_metadata = md.get_item(ebsd_node + ".static_background")
+                if isinstance(static_bg_in_metadata, (da.Array, np.ndarray)):
+                    static_bg = da.asarray(static_bg_in_metadata, chunks="auto")
+                else:
+                    raise ValueError
+            except (AttributeError, ValueError):
+                raise ValueError(
+                    "`static_bg` is not a valid NumPy or Dask array or could not be "
+                    "read from signal metadata"
                 )
         if dtype_out != static_bg.dtype:
             raise ValueError(
-                f"The static background dtype_out {static_bg.dtype} is not the same as "
-                f"pattern dtype_out {dtype_out}."
+                f"Static background dtype_out {static_bg.dtype} is not the same as "
+                f"pattern dtype_out {dtype_out}"
             )
         pat_shape = self.axes_manager.signal_shape[::-1]
         bg_shape = static_bg.shape
         if bg_shape != pat_shape:
-            raise OSError(
-                f"The pattern {pat_shape} and static background {bg_shape} shapes are "
-                "not identical."
+            raise ValueError(
+                f"Signal {pat_shape} and static background {bg_shape} shapes are not "
+                "identical"
             )
         dtype = np.float32
         static_bg = static_bg.astype(dtype)

kikuchipy/signals/tests/test_ebsd.py

@@ -243,10 +243,10 @@ def test_remove_static_background(
             (
                 np.ones((3, 3), dtype=np.int8),
                 ValueError,
-                "The static background dtype_out",
+                "Static background dtype_out",
             ),
-            (None, OSError, "The static background is not a numpy or dask"),
-            (np.ones((3, 2), dtype=np.uint8), OSError, "The pattern"),
+            (None, ValueError, "`static_bg` is not a valid NumPy or Dask array"),
+            (np.ones((3, 2), dtype=np.uint8), ValueError, "Signal"),
         ],
     )
     def test_incorrect_static_background_pattern(
@@ -265,6 +265,12 @@ def test_lazy_remove_static_background(self, dummy_signal, dummy_background):
         dummy_signal.remove_static_background(static_bg=dummy_background)
         assert isinstance(dummy_signal.data, da.Array)
 
+        ebsd_node = kp.signals.util.metadata_nodes("ebsd")
+        dummy_signal.metadata.set_item(
+            ebsd_node + ".static_background", da.from_array(dummy_background)
+        )
+        dummy_signal.remove_static_background()
+
     def test_remove_static_background_scalebg(self, dummy_signal, dummy_background):
         dummy_signal2 = dummy_signal.deepcopy()