title: Similar image search software (like TinEye)
body: <p>In one of our community sites, we allow users to upload images. These images are approved or rejected by our moderators.</p>
  
  <p>To limit the work needed by our administrators, we want to 'log' each picture that is rejected  to some kind of database, and do a lookup in this database prior to submitting an image for approval. If a similar image already has been rejected, the uploaded image won't be submitted for approval.</p>
  
  <p>We can of course just log stuff like filename, size and MD5 of the picture for similarity, but it would definitely we could find differently cropped or resized images.</p>
  
  <p>TinEye.com provides a similar functionality.</p>
  
  <p>Do you know any kind of open-source software capable of this? Do you have any other ideas?</p>
  
  <p>Thanks!</p>