maysamsh / swift-adaptive-imageviewer

An adaptive solution to fit the image within the screen using a UIScrollView and AutoLayout, programatically.

swift-adaptive-imageviewer

An adaptive solution to fit an image within the screen using a UIScrollView and AutoLayout, programatically.

There are lots of other similar projects on the internet, I did another one, why not?

The way it works is simple, creates an UIScrollView programmatically, disables its autoresize, adds necessary constrains to fill the parent view. In the next step, in viewWillLayoutSubviews update the scroll views content size, and calculates insets to fit it into the screen and after a short delay calls setZoomScale method of scroll view.

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    if let image = UIImage(named: "image.jpg") {
        scrollView.contentSize = image.size
        imageView.image = image
        let minZoom = min(self.view.bounds.size.width / image.size.width, self.view.bounds.size.height / image.size.height)
        self.scrollView.minimumZoomScale = minZoom
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
            let vertical = (self.view.bounds.size.height - (image.size.height * minZoom)) / 2
            self.scrollView.contentInset = UIEdgeInsets(top: vertical, left: 0, bottom: vertical, right: 0)
            self.scrollView.setZoomScale(minZoom, animated: true)
        }
    }
}

for the rest of the code, read it yourself.