Merge 12b895e into 3d07924

holoviews/operation/datashader.py

@@ -1511,10 +1511,11 @@ class SpreadingOperation(LinkableOperation):
     to make sparse plots more visible.
     """
 
-    how = param.ObjectSelector(default='source',
-            objects=['source', 'over', 'saturate', 'add'], doc="""
+    how = param.ObjectSelector(default=None,
+            objects=[None, 'source', 'over', 'saturate', 'add', 'max', 'min'], doc="""
         The name of the compositing operator to use when combining
-        pixels.""")
+        pixels. Default of None uses 'over' operator for RGB elements
+        and 'add' operator for aggregate arrays.""")
 
     shape = param.ObjectSelector(default='circle', objects=['circle', 'square'],
                                  doc="""
@@ -1584,7 +1585,9 @@ class spread(SpreadingOperation):
         Number of pixels to spread on all sides.""")
 
     def _apply_spreading(self, array):
-        return tf.spread(array, px=self.p.px, how=self.p.how, shape=self.p.shape)
+        replace_none_how = ds_version <= '0.11.1' and (self.p.how is None)
+        how = 'source' if replace_none_how else self.p.how
+        return tf.spread(array, px=self.p.px, how=how, shape=self.p.shape)
 
 
 class dynspread(SpreadingOperation):
@@ -1611,9 +1614,11 @@ class dynspread(SpreadingOperation):
         allowed.""")
 
     def _apply_spreading(self, array):
+        replace_none_how = ds_version <= '0.11.1' and (self.p.how is None)
+        how = 'source' if replace_none_how else self.p.how
         return tf.dynspread(
             array, max_px=self.p.max_px, threshold=self.p.threshold,
-            how=self.p.how, shape=self.p.shape
+            how=how, shape=self.p.shape
         )