objective-c - AVFoundation:在视频 session 中拍摄高质量静态图像

Question

我正在分析 AVMediaTypeVideo 类型的捕获 session 中的实时图像。如何在某些事件中捕获高质量静态图像(而不是低分辨率样本缓冲区)=

var videoCaptureDevice: AVCaptureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
var device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
var previewLayer: AVCaptureVideoPreviewLayer?    
var captureSession = AVCaptureSession()
let cameraOutput = AVCapturePhotoOutput()


//called in view did load
private func setupCamera() {

    let input = try? AVCaptureDeviceInput(device: videoCaptureDevice)        
    captureSession.sessionPreset = AVCaptureSessionPreset640x480
    if self.captureSession.canAddInput(input) {
        self.captureSession.addInput(input)
    }
    self.previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)


    let videoDataOutput = AVCaptureVideoDataOutput()
    if self.captureSession.canAddOutput(videoDataOutput){
        self.captureSession.addOutput(videoDataOutput)
        videoDataOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
    }

}

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {

 // sampleBuffer is analysed
 // if result is positive, I would like to take a high quality picture

}

Answer 1

这是我在应用程序中使用的一个小片段。我希望这会有所帮助

private func takePhoto() -> Void
{
    if let videoConnection = stillImageOutput!.connection(withMediaType: AVMediaTypeVideo) 
    {
        videoConnection.videoOrientation = AVCaptureVideoOrientation.portrait

        stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler: { (sampleBuffer, error) in
            guard let buffer = sampleBuffer else
            {
                return
            }

            let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
            let dataProvider = CGDataProvider(data: imageData as! CFData)
            let cgImageRef = CGImage(jpegDataProviderSource: dataProvider!, 
                decode: nil, 
                shouldInterpolate: true, 
                intent: CGColorRenderingIntent.defaultIntent)

            // The image taked
            let image: UIImage = UIImage(cgImage: cgImageRef!, scale: 1.0, orientation: UIImageOrientation.right)

            // Detenemos la captura de imagenes
            self.captureSession!.stopRunning()
        })
    }
}

如果您没有设置captureSession变量的sessionPreset属性，默认情况下他的值为AVCapture​Session​Preset​High。唯一高于此的预设是 AVCaptureSessionPresetPhoto