Merge pull request #562 from ANTsX/plot-std-img

fix issue with plotting negative-sum images

ants/viz/plot.py

@@ -228,7 +228,7 @@ def reorient_slice(x, axis):
     if not isinstance(image, iio.ANTsImage):
         raise ValueError("image argument must be an ANTsImage")
 
-    if not image.sum() > 0:
+    if sum(sum(image != 0)) == 0:
         warnings.warn("Image must be non-zero. will not plot.")
         return