Question

我正致力于视频应用。我想在相机自动对焦时丢弃视频帧。在自动聚焦期间，捕获的图像变得模糊，并且该帧的图像处理变差，但是一旦完成自动聚焦，图像处理就变得极好。有人给我解决方案吗？

Answer 1

adjustingFocus财产。
指示设备当前是否正在调整其焦点设置。（只读）

*注意：您可以使用键值观察来观察对此属性值的更改。

iOS 4.0及更高版本

https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html#//apple_ref/occ/instp/AVCaptureDevice/adjustingFocus

Answer 2

Swift 4+上的示例

class ViewController: UIViewController, AVCapturePhotoCaptureDelegate {
    //@objc var captureDevice: AVCaptureDevice?

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            self.addObservers()
        }

       func addObservers() {
             self.addObserver(self, forKeyPath: "captureDevice.adjustingFocus", options: .new, context: nil)

       }

       func removeObservers() {
          self.removeObserver(self, forKeyPath: "captureDevice.adjustingFocus")
       }


      override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey: Any]?, context: UnsafeMutableRawPointer?) {

         if keyPath == "captureDevice.adjustingFocus" {
             print("============== adjustingFocus: \(self.captureDevice?.lensPosition)") 
        }

    } //End of class

Answer 3

以下是Swift 3.x中的示例代码。

首先应在摄像机初始化时将观察者添加到选定的捕获设备。

captureDevice.addObserver(self, forKeyPath: "adjustingFocus", options: [.new], context: nil)

然后重写observeValue方法。通过访问方法返回的可选值，可以识别自动聚焦帧。

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

    guard let key = keyPath, let changes = change else {
        return
    }

    if key == "adjustingFocus" {

        let changedValue = changes[.newKey]
        if (changedValue! as! Bool){ 
            // camera is auto-focussing
        }else{         
            // camera is not auto-focussing
        }
    }
}

检测相机何时自动对焦

3 个答案: