title: Image comparison - fast algorithm
body: <p>I'm looking to create a base table of images and then compare any new images against that to determine if the new image is an exact (or close) duplicate of the base.</p>
  
  <p>For example: if you want to reduce storage of the same image 100's of times, you could store one copy of it and provide reference links to it.  When a new image is entered you want to compare to an existing image to make sure it's not a duplicate ... ideas?</p>
  
  <p>One idea of mine was to reduce to a small thumbnail and then randomly pick 100 pixel locations and compare.</p>