Added pick to zoom feature from #214

Author: AlexLittlejohn

ALCameraViewController/ViewController/CameraViewController.swift

@@ -266,6 +266,7 @@ open class CameraViewController: UIViewController {
         setupActions()
         checkPermissions()
         cameraView.configureFocus()
+        cameraView.configureZoom()
     }
 
     /**

ALCameraViewController/Views/CameraView.swift

@@ -100,6 +100,11 @@ public class CameraView: UIView {
             line.alpha = 0
         }
     }
+
+    public func configureZoom() {
+        let pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(pinch(gesture:)))
+        addGestureRecognizer(pinchGesture)
+    }
 
     internal func focus(gesture: UITapGestureRecognizer) {
         let point = gesture.location(in: self)
@@ -134,6 +139,37 @@ public class CameraView: UIView {
                 }
         })
     }
+
+    internal func pinch(gesture: UIPinchGestureRecognizer) {
+        guard let device = device else { return }
+
+        // Return zoom value between the minimum and maximum zoom values
+        func minMaxZoom(_ factor: CGFloat) -> CGFloat {
+            return min(max(factor, 1.0), device.activeFormat.videoMaxZoomFactor)
+        }
+
+        func update(scale factor: CGFloat) {
+            do {
+                try device.lockForConfiguration()
+                defer { device.unlockForConfiguration() }
+                device.videoZoomFactor = factor
+            } catch {
+                print("\(error.localizedDescription)")
+            }
+        }
+
+        let velocity = gesture.velocity
+        let velocityFactor: CGFloat = 8.0
+        let desiredZoomFactor = device.videoZoomFactor + atan2(velocity, velocityFactor)
+
+        let newScaleFactor = minMaxZoom(desiredZoomFactor)
+        switch gesture.state {
+        case .began, .changed:
+            update(scale: newScaleFactor)
+        case _:
+            break
+        }
+    }
 
     private func createPreview() {