title: Memory leak when resizing UIImage
body: <p>I've read through multiple threads concerning the topic but my problem still persists.
  When I'm resizing an Image with following code:</p>
  
  <pre><code>extension UIImage {
    func thumbnailWithMaxSize(image:UIImage, maxSize: CGFloat) -&gt; UIImage {
      let width = image.size.width
      let height = image.size.height
      var sizeX: CGFloat = 0
      var sizeY: CGFloat = 0
      if width &gt; height {
          sizeX = maxSize
          sizeY = maxSize * height/width
      }
      else {
          sizeY = maxSize
          sizeX = maxSize * width/height
      }
  
      UIGraphicsBeginImageContext(CGSize(width: sizeX, height: sizeY))
      let rect = CGRect(x: 0.0, y: 0.0, width: sizeX, height: sizeY)
      UIGraphicsBeginImageContext(rect.size)
      draw(in: rect)
      let thumbnail = UIGraphicsGetImageFromCurrentImageContext()!;
  
      UIGraphicsEndImageContext()
  
      return thumbnail
  
  }
  
  
  override func viewDidLoad() {
      super.viewDidLoad()
  
      let lionImage = UIImage(named: "lion.jpg")!
  
      var thumb = UIImage()
  
      autoreleasepool {
          thumb = lionImage.thumbnailWithMaxSize(image: lionImage, maxSize: 2000)
      }
      myImageView.image = thumb
  }
  </code></pre>
  
  <p>...the memory is not released. So when I navigate through multiple ViewControllers (e.g. with a PageViewController) I end up getting memory warnings and the app eventually crashes.
  I also tried to load the image via UIImage(contentsOfFile: path) without success.
  Any suggestions? </p>