title: Computing the difference between images
body: <p>Do you guys know of any algorithms that can be used to compute difference between images?</p>
  
  <p>Take this webpage for example <a href="http://tineye.com/" rel="noreferrer">http://tineye.com/</a> You give it a link or upload an image and it finds similiar images. I doubt that it compares the image in question against all of them (or maybe it does).</p>
  
  <p>By compute I mean like what the <a href="http://en.wikipedia.org/wiki/Levenshtein_distance" rel="noreferrer">Levenshtein_distance</a> or the <a href="http://en.wikipedia.org/wiki/Hamming_distance" rel="noreferrer">Hamming distance</a> is for strings.</p>
  
  <p>By no means do I need to the correct answer for a project or anything, I just found the website and got very curious. I know digg pays for a similiar service for their website.</p>