title: Image file structure and encoding filename. like Facebook image Urls
body: <p>I'm wondering whats the best folder structure for a web application to save users images if they have different usernames and different albums. I'm using Amazon S3, folders and buckets</p>
  
  <p>I don't want people to be able to predict the urls for users/albums like FB</p>
  
  <p><a href="http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1189.snc/154140_10150322456245277_731310276_15908482_4918209_n.jpg" rel="nofollow">http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1189.snc/154140_10150322456245277_731310276_15908482_4918209_n.jpg</a></p>
  
  <p>Also for the filename. Whats the best type of information to encode to change the filename to.
  (username, date/time, user id)
  E.g.</p>
  
  <p>Original: 
  apple.jpg</p>
  
  <p>Encoded:
  1263547483_56783929_3934736_943883.jpg</p>
  
  <p>What would you use to encode these Url safe filenames? Base64, MessageDigests?</p>