 against the bounding
box of polygon list <i>a</i> and apply the disjoint-union of that with
polygon list <i>a</i> deflated by some integer amount.&nbsp; The end
result is accumulated into a list of polygons with a union
operation.&nbsp; It is considerably more typing to describe this usage
of the API than to code it, and the description is not much clearer
than the code itself.&nbsp; A picture is worth a thousand words.</p>
      <p><img src="images/foo.PNG" border="0" height="371" width="432" /></p>
     