--- a/make-tile	Thu Aug 26 08:37:46 2021 -0700
+++ b/make-tile	Thu Aug 26 13:50:18 2021 -0700
@@ -116,13 +116,13 @@
     if orientation == Orientation.VERTICAL:
         what = "column"
         strip = Column
-        maxn = image.width - 1
+        maxn = image.width
     else:
         what = "row"
         strip = Row
-        maxn = image.height - 1
+        maxn = image.height
     # Establish outer bound and sanity-check it.
-    outer = 0 if direction == Direction.ASCENDING else maxn
+    outer = 0 if direction == Direction.ASCENDING else maxn - 1
     if not strip(image, outer).is_all_white():
         raise TopoTilerException("Unexpected nonwhite edge ({0} = {1})!".format(what, outer))
     # Establish inner bound and sanity-check it.