How to Zoom In/Out Photo on double Tap in the iPhone WWDC 2010 - 104 PhotoScroller

Question

I am going through the Sample code of iPhone WWDC 2010 - 104 PhotoScroller App. It\'s working great with my project related images (PDF Page Images)

but I am struggl

Answer 1

Swift 3

Normally image zoom functionality is required with both double tap and pinch gesture, so I am providing complete solution to achieve the same. Double tap zoom is inspired by above answers and pinch zoom was taken from here.

import UIKit

class ViewController: UIViewController, UIScrollViewDelegate {

    var imageView: UIImageView!
    var scrollImg: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let vWidth = self.view.frame.width
        let vHeight = self.view.frame.height

        scrollImg = UIScrollView()
        scrollImg.delegate = self
        scrollImg.frame = CGRect(x: 0, y: 0, width: vWidth, height: vHeight)
        scrollImg.backgroundColor = UIColor(red: 90, green: 90, blue: 90, alpha: 0.90)
        scrollImg.alwaysBounceVertical = false
        scrollImg.alwaysBounceHorizontal = false
        scrollImg.showsVerticalScrollIndicator = true
        scrollImg.flashScrollIndicators()

        scrollImg.minimumZoomScale = 1.0
        scrollImg.maximumZoomScale = 10.0

        let doubleTapGest = UITapGestureRecognizer(target: self, action: #selector(handleDoubleTapScrollView(recognizer:)))
        doubleTapGest.numberOfTapsRequired = 2
        scrollImg.addGestureRecognizer(doubleTapGest)

        self.view.addSubview(scrollImg)

        imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: vWidth, height: vHeight))
        imageView.image = UIImage(named: "cat")
        imageView!.layer.cornerRadius = 11.0
        imageView!.clipsToBounds = false
        scrollImg.addSubview(imageView!)
    }

    func handleDoubleTapScrollView(recognizer: UITapGestureRecognizer) {
        if scrollImg.zoomScale == 1 {
            scrollImg.zoom(to: zoomRectForScale(scale: scrollImg.maximumZoomScale, center: recognizer.location(in: recognizer.view)), animated: true)
        } else {
            scrollImg.setZoomScale(1, animated: true)
        }
    }

    func zoomRectForScale(scale: CGFloat, center: CGPoint) -> CGRect {
        var zoomRect = CGRect.zero
        zoomRect.size.height = imageView.frame.size.height / scale
        zoomRect.size.width  = imageView.frame.size.width  / scale
        let newCenter = imageView.convert(center, from: scrollImg)
        zoomRect.origin.x = newCenter.x - (zoomRect.size.width / 2.0)
        zoomRect.origin.y = newCenter.y - (zoomRect.size.height / 2.0)
        return zoomRect
    }

    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return self.imageView
    }

}