UIScrollView Zooming & contentInset

Question

Simliar to iOS Photos App where the user is zooming in and out of an image by pinching:

UIView > UIScrollView > UIImageView > UIImage

Initially, I had the issue

Answer 1

Your approach looks correct. You need to update your code as below.

    func scrollViewDidZoom(scrollView: UIScrollView) {

    if scrollView.zoomScale > 1 {

        if let image = imageView.image {

            let ratioW = imageView.frame.width / image.size.width
            let ratioH = imageView.frame.height / image.size.height

            let ratio = ratioW < ratioH ? ratioW:ratioH

            let newWidth = image.size.width*ratio
            let newHeight = image.size.height*ratio

            let left = 0.5 * (newWidth * scrollView.zoomScale > imageView.frame.width ? (newWidth - imageView.frame.width) : (scrollView.frame.width - scrollView.contentSize.width))
            let top = 0.5 * (newHeight * scrollView.zoomScale > imageView.frame.height ? (newHeight - imageView.frame.height) : (scrollView.frame.height - scrollView.contentSize.height))

            scrollView.contentInset = UIEdgeInsetsMake(top, left, top, left)
        }
    } else {
        scrollView.contentInset = UIEdgeInsetsZero
    }
}