fl034

@objc func handleDoubleTap(_ recognizer: UITapGestureRecognizer) {
    let scale = min(scrollView.zoomScale * 2, scrollView.maximumZoomScale)

    if scrollView.zoomScale == scrollView.minimumZoomScale { // zoom in
                let point = recognizer.location(in: imageView)
                
                let scrollSize = scrollView.frame.size
                let zoomScale = scrollView.maximumZoomScale * 0.7
                let size = CGSize(width: scrollSize.width / zoomScale,
                                  height: scrollSize.height / zoomScale)

fl034

import UIKit

// known-good: Xcode 8.2.1
/**
 
 UIImageView subclass which works with Auto Layout to try
 to maintain the same aspect ratio as the image it displays.
 
 This is unlike the usual behavior of UIImageView, where the
 scaleAspectFit content mode only affects what the view displays