import UIKit

class ViewController: UIViewController, UIScrollViewDelegate {

    let imageView = UIImageView(image: UIImage(named: "My Image"))

    @IBOutlet weak var scrollView: UIScrollView! {
        didSet {
            scrollView.delegate = self
            scrollView.addGestureRecognizer(UIRotationGestureRecognizer(target: self, action: "rotation:"))
            scrollView.contentSize = imageView.frame.size

            scrollView.addSubview(imageView)

            scrollView.maximumZoomScale = 5.0

            let heightScale = UIScreen.mainScreen().bounds.height / imageView.frame.size.height
            let widthScale = UIScreen.mainScreen().bounds.width / imageView.frame.size.width
            scrollView.minimumZoomScale = min(heightScale, widthScale)
        }
    }

    func rotation(recognizer: UIRotationGestureRecognizer) {
        switch recognizer.state {
        case .Changed:
            imageView.transform = CGAffineTransformMakeRotation(lastAngle + recognizer.rotation)
        case .Ended:
            lastAngle += recognizer.rotation
        default:
            break
        }
    }

    var lastAngle: CGFloat = 0

    func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}