title: Filter camera roll, in order to upload only specified pictures
body: <p>My app generates pictures from iphone camera.
  I have an upload feature in-app.
  I want the user to be able to upload through my app, only the pictures generated by it.</p>
  
  <p>So far, i found 2 ways of doing it :</p>
  
  <p>record and store assetURL in a DB for comparison
  or
  write my own metadata in user_comment in EXIF. And retrieve it with assetForURL.</p>
  
  <p>I prefer the second option but it seems that it works only if the user allows geotaging ?!!
  This type of thing could scare the client don't you think ?</p>
  
  <p>Any idea about how to deal with this problem ?</p>