UIScrollView scrolls out of image after image is zoomed in? - ios

Question

I'm trying to implement a image zooming functionality using UIScrollview. where as I kept image as aspect fit.
Image is inside a UIScrollView, and image frame has been given similar to UIScrollView.
Here is my code.
override func viewDidLoad()
{
super.viewDidLoad()
// Do any additional setup after loading the view.
scroller.minimumZoomScale = 1.0
scroller.maximumZoomScale = 7.0
}
// MARK: - User Defined Methods
#IBAction func doubleTapGestureAction(_ sender: UITapGestureRecognizer)
{
if scroller.zoomScale == 1
{
scroller.zoom(to: zoomForScale(scale: scroller.maximumZoomScale, center: sender.location(in: sender.view)), animated: true)
}
else
{
scroller.setZoomScale(1, animated: true)
}
print(isZoomedIn)
}
func zoomForScale(scale: CGFloat, center: CGPoint) -> CGRect
{
var zoomRect = CGRect.zero
zoomRect.size.height = image.frame.size.height / scale
zoomRect.size.width = image.frame.size.width / scale
let newCenter = image.convert(center, from: scroller)
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 image
}

Answer 1

Here is sample code:
import UIKit
class ViewController: UIViewController,UIScrollViewDelegate {
var imgDemo: UIImageView = {
let img = UIImageView()
img.contentMode = .scaleAspectFill
img.isUserInteractionEnabled = true
return img
}()
var scrollView:UIScrollView = {
let scroll = UIScrollView()
scroll.maximumZoomScale = 4.0
scroll.minimumZoomScale = 0.25
scroll.clipsToBounds = true
return scroll
}()
override func viewDidLoad() {
super.viewDidLoad()
imgDemo.frame = CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height)
imgDemo.image = UIImage(named: "5.jpg")
scrollView.delegate = self
scrollView.frame = imgDemo.frame
scrollView.addSubview(imgDemo)
view.addSubview(scrollView)
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return imgDemo
}
}

Answer 2

Take a look at these methods. May be it will help. I have scroll view stretched to controller's view size. customizeScrollView() will calculate min and max scale options. centerImageView() will put UIImageView in the center of your UIScrollView
Call the customizeScrollView function in viewDidload.
fileprivate func customizeScrollView() {
guard let image = imageView?.image else { return }
var minZoom = fmin(self.view.frame.width / image.size.width, self.view.frame.height / image.size.height)
minZoom = fmin(1.0, minZoom)
scrollView?.contentSize = image.size
scrollView?.minimumZoomScale = minZoom
scrollView?.addSubview(self.imageView!)
scrollView?.setZoomScale(minZoom, animated: false)
centerImageView()
}
fileprivate func centerImageView() {
guard let imageView = imageView else { return }
guard let scrollView = scrollView else { return }
let boundsSize = scrollView.bounds.size
var frameToCenter = imageView.frame
// Center horizontally
if frameToCenter.size.width < boundsSize.width {
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2
} else {
frameToCenter.origin.x = 0
}
// Center vertically
if frameToCenter.size.height < boundsSize.height {
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2
} else {
frameToCenter.origin.y = 0
}
imageView.frame = frameToCenter
}
public func scrollViewDidZoom(scrollView: UIScrollView) {
print(imageView.frame)
centerImageView()
}