Merge pull request #767 from jimofthecorn/develop

fixed bug in graphicsItems/ImageItem.py: degenerate images (max==min)

pyqtgraph/graphicsItems/ImageItem.py

@@ -487,6 +487,9 @@ class ImageItem(GraphicsObject):
         if bins == 'auto':
             mn = np.nanmin(stepData)
             mx = np.nanmax(stepData)
+            if mx == mn:
+                # degenerate image, arange will fail
+                mx += 1
             if np.isnan(mn) or np.isnan(mx):
                 # the data are all-nan
                 return None, None