title: How to combine images in Ruby
body: <p>I have 4 square images, 1,2,3 and 4 each with 2048x2048px.</p>
  
  <p>I need to combine those into a 4096x4096px image, like this:</p>
  
  <pre><code> 1 2
   3 4
  </code></pre>
  
  <p>Right now I am doing this manually with Gimp, but the amount processing is growing and I would like to implement an automated solution.</p>
  
  <p>Is there an easy way to do this in Ruby? (Rails gem would be ok or any shell command that can be run from inside a Rails app) </p>