Added ability to control zoom factor when available and added ability…

… to example.

Note: this only works on Photo preset.

CameraEngine/CameraEngine.swift

@@ -157,6 +157,23 @@ public class CameraEngine: NSObject {
         }
     }
 
+    private var _cameraZoomFactor: CGFloat = 1.0
+    public var cameraZoomFactor: CGFloat! {
+        get {
+            if let `captureDevice` = captureDevice {
+                _cameraZoomFactor = captureDevice.videoZoomFactor
+            }
+
+            return self._cameraZoomFactor
+        }
+        set {
+            let newZoomFactor = self.cameraDevice.changeCurrentZoomFactor(newValue)
+            if newZoomFactor > 0 {
+                self._cameraZoomFactor = newZoomFactor
+            }
+        }
+    }
+
     public var blockCompletionBuffer: blockCompletionOutputBuffer? {
         didSet {
             self.cameraOutput.blockCompletionBuffer = self.blockCompletionBuffer

CameraEngine/CameraEngineDevice.swift

@@ -62,6 +62,24 @@ class CameraEngineDevice {
         }
     }
 
+    func changeCurrentZoomFactor(newFactor: CGFloat) -> CGFloat {
+        var zoom: CGFloat = 1.0
+        if let currentDevice = self.currentDevice {
+            do {
+                try currentDevice.lockForConfiguration()
+                zoom = max(1.0, min(newFactor, currentDevice.activeFormat.videoMaxZoomFactor))
+                currentDevice.videoZoomFactor = zoom
+                currentDevice.unlockForConfiguration()
+            }
+            catch {
+                zoom = -1.0
+                fatalError("[CameraEngine] error, impossible to lock configuration device")
+            }
+        }
+
+        return zoom
+    }
+
     func changeCurrentDevice(position: AVCaptureDevicePosition) {
         self.currentPosition = position
         switch position {

ExampleProject/CameraEngineExample/ViewController.swift

@@ -270,5 +270,18 @@ class ViewController: UIViewController {
         self.cameraEngine.blockCompletionCodeDetection = { codeObject in
             print("code object value : \(codeObject.stringValue)")
         }
+
+        let twoFingerPinch = UIPinchGestureRecognizer(target: self, action: #selector(ViewController.onTwoFingerPinch(_:)))
+        self.view.addGestureRecognizer(twoFingerPinch)
+        self.view.userInteractionEnabled = true
+    }
+
+    @objc func onTwoFingerPinch(recognizer: UIPinchGestureRecognizer) {
+        let maxZoom: CGFloat = 6.0
+        let pinchVelocityDividerFactor: CGFloat = 5.0
+        if recognizer.state == .Changed {
+            let desiredZoomFactor = min(maxZoom, cameraEngine.cameraZoomFactor + atan2(recognizer.velocity, pinchVelocityDividerFactor))
+            cameraEngine.cameraZoomFactor = desiredZoomFactor
+        }
     }
 }