Swift5：从相机获取brightness/light级

Question

我有这段代码，它是 AVCaptureMetadataOutputObjectsDelegate 的扩展：

internal func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
        guard let captureSession = captureSession else { return }
        captureSession.stopRunning()
        if let metadataObject = metadataObjects.first {
            guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
            guard let stringValue = readableObject.stringValue else { return }
            AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
            found(code: stringValue)
        }
    }

并在'views'一个二维码时被调用：

let metadataOutput = AVCaptureMetadataOutput()
        
        if (captureSession.canAddOutput(metadataOutput)) {
            captureSession.addOutput(metadataOutput)
            metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            metadataOutput.metadataObjectTypes = [.qr]

我想做的是增加一个新的功能，就是一打开相机就知道后置摄像头的亮度是多少。

我到处都发现他们用这个：

func captureOutput(_ output: AVCaptureOutput, 
                  didOutput sampleBuffer: CMSampleBuffer, 
                       from connection: AVCaptureConnection)

但在我看来它已经不在 AvFoundation 中了。

Answer 1

我假设您提到的相机的“光度”是某种光照级别指标。我知道几种测量方法。

我想，您的代码中一定已经定义了一个 videoDevice：let videoDevice: AVCaptureDevice。如果不单独存放，从videoInput.videoDevice.

获取

勾选videoDevice.iso。值越低 - 照明条件越亮。这是一个KVO 属性，所以你可以实时观察它的变化。
勾选videoDevice.exposureDuration。相同：较低的值 → 更亮的照明条件。曝光时间基本上是 iOS 系统相机为了更好的夜间模式拍摄而调整的时间。
如您所述，您还可以从相机获取实时像素缓冲区以进行分析。喜欢构建直方图并将亮像素与暗像素进行比较等

在你的相机里class:

/// You already have the session
private let session = AVCaptureSession()

/// Define a video output (probably you did that already, 
/// otherwise how would your camera scan QRs at all)
private let videoOutput = AVCaptureVideoDataOutput()

/// Define a queue for sample buffer
private let videoSampleBufferQueue = DispatchQueue(label: "videoSampleBufferQueue")

然后将输出添加到会话：

if session.canAddOutput(videoOutput){
    session.addOutput(videoOutput)
}
videoOutput.setSampleBufferDelegate(self, queue: videoSampleBufferQueue)

并执行 AVCaptureVideoDataOutputSampleBufferDelegate:

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
    // Handle the pixelBuffer the way you like
}

Swift5：从相机获取brightness/light级

Swift5: obtain brightness/light level from the camera

swift

camera

qr-code