title: Detecting image differences
body: <p>I have three images:</p>
  
  <p><img src="https://i.stack.imgur.com/r5Afy.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/Um1ZD.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/pI5ig.png" alt="enter image description here"></p>
  
  <p>I've aligned them spatio-temporally to the best of my ability.  I want to detect where the <strong>content-specific</strong> differences (the caption, the RT logo) are.  Simple image difference (followed by thresholding, etc) doesn't work here for a couple of reasons:</p>
  
  <ul>
  <li>the first image is quite blurry.  Image difference will yield peaks at edges.  I don't want that</li>
  <li>the first image has undergone some sort of color transformation, so the difference contains a lot of information that I don't need</li>
  </ul>
  
  <p>Here's the plain image difference between the first two images (using GIMP):</p>
  
  <p><img src="https://i.stack.imgur.com/0fdMy.png" alt="enter image description here"></p>
  
  <p>Any ideas?</p>