Add iOS

ios/Extensions/AVCaptureDevice+neutralZoom.swift

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+//
+//  AVCaptureDevice+neutralZoom.swift
+//  Cuvent
+//
+//  Created by Marc Rousavy on 10.01.21.
+//  Copyright © 2021 Facebook. All rights reserved.
+//
+
+import AVFoundation
+
+extension AVCaptureDevice {
+  var neutralZoomFactor: CGFloat {
+    if #available(iOS 13.0, *) {
+      if let indexOfWideAngle = self.constituentDevices.firstIndex(where: { $0.deviceType == .builtInWideAngleCamera }) {
+        if let zoomFactor = self.virtualDeviceSwitchOverVideoZoomFactors[safe: indexOfWideAngle - 1] {
+          return CGFloat(zoomFactor.doubleValue)
+        }
+      }
+    }
+    return 1.0
+  }
+
+  /**
+   Get the value at which the Zoom value is neutral, in percent (0.0-1.0)
+
+   * On single-camera physical devices, this value will always be 0.0
+   * On devices with multiple cameras, e.g. triple-camera, this value will be a value between 0.0 and 1.0, where the field-of-view and zoom looks "neutral"
+   */
+  var neutralZoomPercent: CGFloat {
+    return (neutralZoomFactor - minAvailableVideoZoomFactor) / (maxAvailableVideoZoomFactor - minAvailableVideoZoomFactor)
+  }
+}