   @IBOutlet weak var thresholdSlider: UISlider!
   @IBAction func handleThresholdSliderChanged(sender: UISlider) {
     updateOutputImage()
+    includesChanges = true
   }
   
   override func viewDidLoad() {

  var shouldShowCancelConfirmation: Bool {
    // Determines whether a confirmation to discard changes should be shown to the user on cancel.
    // (Typically, this should be "true" if there are any unsaved changes.)
    return false
  }
  
  func cancelContentEditing() {

class PhotoEditingViewController: UIViewController, PHContentEditingController {
  
  let filter = ChromaKeyFilter()
  var includesChanges = false
  var input: PHContentEditingInput?
  let formatIdentifier = "com.shinobicontrols.chromakey"
  let formatVersion    = "1.0"
