title: Querying, Editing and removing image metadata in ios
body: <p>OK, I'm new to IOS development but have a decent amount of programming experience so thought it would be fairly straightforward to pick up. </p>
  
  <p>I'm creating a photo app that will display all of the users images (or take new images using camera) and then display them in galleries based on metadata tags.</p>
  
  <p>I've spent a considerable amount of time searching for the best approach but seems nothing is that suitable, I need to be able to easily access the tags as they will be used as criteria for querying the database and populating the galleries.</p>
  
  <p>The problem is that I want to be able to add extra tags to an image or multiple images at any time without having to parse XMP data and storing an entirely new image.</p>
  
  <p>From what i've found so far there should be ways to add tags to my image file using either XMP or EXIF data to store extra strings but they seem to be quite long-winded, I was considering just making a custom data type that would hold an image and an array of strings for the tags but this doesn't seem logical if there is already a specific structure within the image to store such metadata.</p>
  
  <p>Alot of people have mentioned using
   WriteImageDataToSavedPhotosAlbum or 
   CGImageDestinationSetProperties</p>
  
  <p>Ultimately I would just like to know if anybody can clarify how I should access, edit and display the xXMP or EXIF data in my app or just create my own (shoddy looking) data structure that would essentially be image representation + string array of 'tags'</p>