title: drawing a line on an image with PIL
body: <p>I want to draw a line and show it.
  assume I have a PIL image.</p>
  
  <pre><code>draw = ImageDraw.Draw(pilImage)
  draw.line((100,200, 150,300), fill=128)
  </code></pre>
  
  <p>How can I show the image?  Before drawing the line I could do:</p>
  
  <pre><code>imshow(pilImage)
  </code></pre>
  
  <p>but <code>imshow(draw)</code> does not show the image.</p>
  
  <p>How do I convert this back to a PIL image?</p>