UIImageView pinch zoom swift

Question

I was hoping someone could help me out. I am trying to allow a user to pinch zoom on a UIImageView(with a max and min level allowed). But for some reason the it does not wor

Answer 1

UIImageView pinch zoom with UIScrollView || image zooming ios in swift 3 and Xcode 8 letter Youtube video URL

set uiscrollview Delegate in storyboard

 class PhotoDetailViewController: UIViewController, UIScrollViewDelegate {

    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var imgPhoto: UIImageView!
      
    override func viewDidLoad() {
        
        super.viewDidLoad()
    
        scrollView.minimumZoomScale = 1.0
        scrollView.maximumZoomScale = 6.0        
        // scrollView.delegate = self - it is set on the storyboard.
    }  
        
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
       
        return imgPhoto
    }

Answer 2

Using Swift 5.0, here is how it works for me:

let myImageView = UIImageView(image: myImage)
myImageView.isUserInteractionEnabled = true
let pinchMethod = UIPinchGestureRecognizer(target: self, action: #selector(pinchImage(sender:)))
myImageView.addGestureRecognizer(pinchMethod)

@objc func pinchImage(sender: UIPinchGestureRecognizer) {
  guard let sender.view != nil else { return }

if let scale = (sender.view?.transform.scaledBy(x: sender.scale, y: sender.scale)) {
  guard scale.a > 1.0 else { return }
  guard scale.d > 1.0 else { return }
  sender.view?.transform = scale
  sender.scale = 1.0
 }
}

You can use scale.a, scale.b, scale.c, scale.d, scale.tx and scale.ty to set your scale limits.

Answer 3

I ended up here, probably searching the wrong way.

I was after having my imageView in contentMode = .centre. But I was judging it too zoomed in and I was searching a way to zoom it out. Here's how:

    self.imageView.contentScaleFactor = 3

1 is as if you were doing anything. More that 1 zooms out... 3 works for me but you need to test it out.

Answer 4

You can use ImageScrollView open source, a zoomable and scrollable image view. http://github.com/huynguyencong/ImageScrollView

Like this opensource, add ImageView to ScrollView

open class ImageScrollView: UIScrollView {
   var zoomView: UIImageView? = nil
}

extension ImageScrollView: UIScrollViewDelegate{

    public func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return zoomView
    }

    public func scrollViewDidZoom(_ scrollView: UIScrollView) {
        adjustFrameToCenter()
    }
}

Answer 5

Swift 3 solution

By default UIImageView's userInteration is disabled. Enable it before adding any gestures in UIImageView.

imgView.isUserInteractionEnabled = true

The scale factor relative to the points of the two touches in screen coordinates

var lastScale:CGFloat!
func zoom(gesture:UIPinchGestureRecognizer) {
    if(gesture.state == .began) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = gesture.scale
    }
    if (gesture.state == .began || gesture.state == .changed) {
    let currentScale = gesture.view!.layer.value(forKeyPath:"transform.scale")! as! CGFloat
    // Constants to adjust the max/min values of zoom
    let kMaxScale:CGFloat = 2.0
    let kMinScale:CGFloat = 1.0
    var newScale = 1 -  (lastScale - gesture.scale)
    newScale = min(newScale, kMaxScale / currentScale)
    newScale = max(newScale, kMinScale / currentScale)
    let transform = (gesture.view?.transform)!.scaledBy(x: newScale, y: newScale);
    gesture.view?.transform = transform
    lastScale = gesture.scale  // Store the previous scale factor for the next pinch gesture call
  }
}

Answer 6

In my view, the problem is your determination of currentScale. It always equals 1, because you change the scale of your imageView. You should assign your currentScale as follows:

let currentScale = self.imageView?.frame.size.width / self.imageView?.bounds.size.width