如何實現捏捏放大相機（Swift 3）？

Question

我想實現一個簡單的捏縮放手勢在QR應用程序。
它似乎很簡單，所以我做了一些研究，我發現了一些可能的答案的問題：

AVCaptureDevice Camera Zoom
How to implement "pinch to zoom" in custom camera
Pinch to zoom camera
Zooming while capturing video using AVCapture in iOS

不幸的是無那些真正解決它，因爲我想要的， 我個人喜歡第一個（在Objective-C中），我試圖在Swift 3中完成它。

我發佈了一個答案h上我想出了一些嘗試後的代碼，其他的更容易/更好/更簡單的解決方案，歡迎:)

Answer 1

我從故事板中使用的Pinch Gesture Recognizer，再掛這個動作：

@IBAction func pinchToZoom(_ sender: UIPinchGestureRecognizer) { 

     guard let device = captureDevice else { return } 

     if sender.state == .changed { 

      let maxZoomFactor = device.activeFormat.videoMaxZoomFactor 
      let pinchVelocityDividerFactor: CGFloat = 5.0 

      do { 

       try device.lockForConfiguration() 
       defer { device.unlockForConfiguration() } 

       let desiredZoomFactor = device.videoZoomFactor + atan2(sender.velocity, pinchVelocityDividerFactor) 
       device.videoZoomFactor = max(1.0, min(desiredZoomFactor, maxZoomFactor)) 

      } catch { 
       print(error) 
      } 
     } 
    } 

注意captureDevice是類AVCaptureDevice的可選對象。

Answer 2

@IBAction func pinchToZoom(_ sender: UIPinchGestureRecognizer) { 

    guard let device = captureDevice else { return } 

    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 { 
     debugPrint(error) 
    } 
    } 

    let newScaleFactor = minMaxZoom(pinch.scale * zoomFactor) 

    switch sender.state { 
    case .began: fallthrough 
    case .changed: update(scale: newScaleFactor) 
    case .ended: 
     zoomFactor = minMaxZoom(newScaleFactor) 
     update(scale: zoomFactor) 
    default: break 
    } 
}