title: Extending an image (PIL/Pillow)
body: <p>I can use the following code to draw a black strip (or rectangle) atop a base image:</p>
  
  <pre><code>base_width, base_height = img.size
  background = Image.new('RGBA', (base_width, base_height/3),(0,0,0,146))
  offset = (0,base_height/2)
  img.paste(background,offset,mask=background)
  </code></pre>
  
  <p>Result:</p>
  
  <p><a href="https://i.stack.imgur.com/WaIAD.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WaIAD.jpg" alt="enter image description here"></a></p>
  
  <p>But how do I extend the height of the image such that the said black strip appears attached below the image's bottom border, <em>outside the image itself</em>? </p>
  
  <p>If I move the <code>offset</code> in my code above, the black strip can't move beyond the borders of the base image, so that's not a viable solution. </p>