如何实现相机缩放(Swift 3)？

Question

我想实现一个简单的捏缩放姿态在一个QR应用程序。

这似乎很简单，所以我做了一些研究，找到了一些解决这个问题的可能答案：

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，没有一个真正解决了我想要的问题，我个人喜欢第一个(在Objective中)，我试着用Swift 3来解决它。

我用我想出的代码发布了一个答案，经过一些尝试，其他更简单/更好/更简单的解决方案都受到欢迎:)

Answer 1

我使用了故事板中的Pinch Gesture Recognizer，然后链接到这个操作：

@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是类AVCaptureDevice的一个可选对象。

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(sender.scale * zoomFactor)

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