IGGesture-ViewController.swift

import Foundation
import UIKit

class ViewController: UIViewController {
  // MARK: - UI Initialization
  
  // The image that we will zoom/drag
  var imageView = UIImageView()
  
  // The dark overlay layer behind the image
  // that will be visible while gestures are recognized
  var overlay: UIView = {
    let view = UIView(frame: UIScreen.main.bounds);
    
    view.alpha = 0
    view.backgroundColor = .black
    
    return view
  }()
  
  // Let's start
  override func viewDidLoad() {
    super.viewDidLoad()

    // Do not forget to enable user interaction on our imageView
    imageView.isUserInteractionEnabled = true

    // MARK: - UIGesturesRecognizers
    let pinch = UIPinchGestureRecognizer(target: self, action: #selector(handlePinchGesture))
    let pan = UIPanGestureRecognizer(target: self, action: #selector(handlePanGesture))

    // Use 2 thingers to move the view
    pan.minimumNumberOfTouches = 2
    pan.maximumNumberOfTouches = 2

    // We delegate gestures so we can 
    // perform both at the same time
    pan.delegate = self
    pinch.delegate = self

    // Add the gestures to our target (imageView)
    imageView.addGestureRecognizer(pinch)
    imageView.addGestureRecognizer(pan)

    // Here some basic setup
    view.addSubView(overlay)
    view.bringSubViewToFront(imageView)
  }
  
  /// Setup imageView
  private func setupImageView() {

      // Set the image
      imageView.image = UIImage(named: "your-asset-name-here")

      // Resize the content
      imageView.contentMode = .scaleAspectFill
      imageView.layer.masksToBounds = true

      // That was for testing porpouse only
      // imageView.backgroundColor = .red
      // Constraints
      setupImageViewConstraints()
  }

  /// Setup ImageView constraints
  private func setupImageViewConstraints() {

    // Disable Autoresizing Masks into Constraints
    imageView.translatesAutoresizingMaskIntoConstraints = false

    // Constraints
    NSLayoutConstraint.activate([
        imageView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        imageView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        imageView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        imageView.heightAnchor.constraint(equalToConstant: 250)
    ])

    view.layoutIfNeeded()
  }
}


// MARK: - Extension
extension ViewController: UIGestureRecognizerDelegate {
  
    // That method make it works
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }
    
    @objc func handleZoom(_ gesture: UIPinchGestureRecognizer) {
        switch gesture.state {
        case .began, .changed:
            
            // Only zoom in, not out
            if gesture.scale >= 1 {
              
                // Get the scale from the gesture passed in the function
                let scale = gesture.scale
              
                // use CGAffineTransform to transform the imageView
                gesture.view!.transform = CGAffineTransform(scaleX: scale, y: scale)
            }
          

            // Show the overlay
            UIView.animate(withDuration: 0.2) {
                self.overlay.alpha = 0.8
            }
            break;
        default:
            // If the gesture has cancelled/terminated/failed or everything else that's not performing
            // Smoothly restore the transform to the "original"
            UIView.animate(withDuration: 0.25, delay: 0, options: .curveEaseInOut, animations: {
              gesture.view!.transform = .identity
            }) { _ in
              // Hide the overlay
              UIView.animate(withDuration: 0.2) {
                self.overlay.alpha = 0
              }
            }
        }
    }
    
    @objc func handlePan(_ gesture: UIPanGestureRecognizer) {
        switch gesture.state {
        case .began, .changed:
            // Get the touch position
            let translation = gesture.translation(in: imageView)
            
            // Edit the center of the target by adding the gesture position
            gesture.view!.center = CGPoint(x: imageView.center.x + translation.x, y: imageView.center.y + translation.y)
            gesture.setTranslation(.zero, in: imageView)

            // Show the overlay
            UIView.animate(withDuration: 0.2) {
                self.overlay.alpha = 0.8
            }
            break;
        default:
            // If the gesture has cancelled/terminated/failed or everything else that's not performing
            // Smoothly restore the transform to the "original"
            UIView.animate(withDuration: 0.25, delay: 0, options: .curveEaseInOut, animations: {
                gesture.view!.center = self.view.center
                gesture.setTranslation(.zero, in: self.background)
            }) { _ in
              // Hide the overaly
              UIView.animate(withDuration: 0.2) {
                self.overlay.alpha = 0
              }
            }
            break
        }
    }
}