title: Composite another image, but with margin/padding
body: <p>I am currently doing the following to overlay a large image onto another:</p>
  
  <pre><code>$ convert orig.png overlay.png -gravity center -composite new.png
  </code></pre>
  
  <p>overlay.png is large and really just a semi-transparent texture. </p>
  
  <p>But in some cases I'd like to have a 1 pixel sized margin around the overlay. So:</p>
  
  <pre><code>+--------------+
  |  +--------+  |
  |  | Overlay|  |
  |  +--------+  |
  +--------------+
  </code></pre>
  
  <p>Is this possible?</p>