add swipe gestures, add alan kay

sample/mustache/app/mustache_view_controller.rb

@@ -5,20 +5,38 @@ class MustacheViewController < UIViewController
   end
 
   def viewDidLoad
-    view.image = UIImage.imageNamed('matz.jpg')
+    @images = %w{matz guido kay jmccolor}.map { |name| UIImage.imageNamed(name + '.jpg') }
+    view.image = @images.first
     view.contentMode = UIViewContentModeScaleAspectFit
+    view.userInteractionEnabled = true
+
+    previousGesture = UISwipeGestureRecognizer.alloc.initWithTarget(self, action:'swipePreviousGesture:')
+    previousGesture.direction = UISwipeGestureRecognizerDirectionLeft
+    view.addGestureRecognizer(previousGesture)
+    nextGesture = UISwipeGestureRecognizer.alloc.initWithTarget(self, action:'swipeNextGesture:')
+    nextGesture.direction = UISwipeGestureRecognizerDirectionRight
+    view.addGestureRecognizer(nextGesture)
   end
 
   def viewDidAppear(animated)
+    mustachify
+  end
+
+  def mustachify
+    # Remove previous mustaches.
+    view.subviews.each { |v| v.removeFromSuperview }
+
     # CoreImage used a coordinate system which is flipped on the Y axis
     # compared to UIKit. Also, a UIImageView can return an image larger than
     # itself. To properly translate points, we use an affine transform.
     transform = CGAffineTransformMakeScale(view.bounds.size.width / view.image.size.width, -1 * (view.bounds.size.height / view.image.size.height))
     transform = CGAffineTransformTranslate(transform, 0, -view.image.size.height)
 
-    @detector ||= CIDetector.detectorOfType CIDetectorTypeFace, context:nil, options: { CIDetectorAccuracy: CIDetectorAccuracyHigh }
     image = CIImage.imageWithCGImage(view.image.CGImage)
+    @detector ||= CIDetector.detectorOfType CIDetectorTypeFace, context:nil, options: { CIDetectorAccuracy: CIDetectorAccuracyHigh }
     @detector.featuresInImage(image).each do |feature|
+      # We need the mouth and eyes positions to determine where the mustache
+      # should be added.
       next unless feature.hasMouthPosition and feature.hasLeftEyePosition and feature.hasRightEyePosition
 
       if @debug_face
@@ -31,27 +49,51 @@ class MustacheViewController < UIViewController
         end
       end
 
+      # Create the mustache view.
       mustacheView = UIImageView.alloc.init
       mustacheView.image = UIImage.imageNamed('mustache')
       mustacheView.contentMode = UIViewContentModeScaleAspectFit
 
+      # Compute its location and size, based on the position of the eyes and
+      # mouth. 
       w = feature.bounds.size.width
       h = feature.bounds.size.height / 5
       x = (feature.mouthPosition.x + (feature.leftEyePosition.x + feature.rightEyePosition.x) / 2) / 2 - w / 2
       y = feature.mouthPosition.y
-
       mustacheView.frame = CGRectApplyAffineTransform([[x, y], [w, h]], transform)
 
+      # Apply a rotation on the mustache, based on the face inclination.
       mustacheAngle = Math.atan2(feature.leftEyePosition.x - feature.rightEyePosition.x, feature.leftEyePosition.y - feature.rightEyePosition.y) + Math::PI/2
       mustacheView.transform = CGAffineTransformMakeRotation(mustacheAngle) 
- 
+
       view.addSubview(mustacheView)
     end
   end
 
   def shouldAutorotateToInterfaceOrientation(*)
-    view.subviews.each { |v| v.removeFromSuperview }
-    viewDidAppear(true)
+    mustachify
     true
   end
+
+  def swipePreviousGesture(gesture)
+    idx = @images.index(view.image)
+    view.image =
+      if idx == 0
+        @images.last
+      else
+        @images[idx - 1]
+      end
+    mustachify
+  end
+
+  def swipeNextGesture(gesture)
+    idx = @images.index(view.image)
+    view.image =
+      if idx == @images.size - 1
+        @images.first
+      else
+        @images[idx + 1]
+      end
+    mustachify
+  end
 end