swift - 相机输入的尺寸为一像素一像素

Question

这是一个相当奇怪的请求，但我希望构建一个具有实时摄像头占据整个屏幕的应用程序。但是，它不会显示正常分辨率，而是全部为一种颜色。特别是，我想采用通常是屏幕上中间像素的颜色，并使其占据整个屏幕。它需要实时快速地完成。

我尝试创建一个函数，将 capturesession 保存为 uiimage，然后从中获取像素数据，但是，事实证明它实时速度很慢。有什么建议吗？

Answer 1

假设您有 AVCaptureSession 设置。您需要设置 AVCaptureVideoDataOutput，然后设置其示例缓冲区委托(delegate)。委托(delegate)类应该覆盖 func captureOutput(AVCaptureOutput!, CMSampleBuffer!, AVCaptureConnection!) 。在此函数中，您可以访问像素缓冲区以对中心点进行采样。你可以按照下面的方法来做。我已将中心点的实际采样留给了您。

class MyClass : NSObject, AVCaptureVideoDataOutputSampleBufferDelegate {

    func addVideoOutput() {
        // Add video data output.
        if session.canAddOutput(videoDataOutput)
        {
            videoDataOutput.setSampleBufferDelegate(self, queue: sessionQueue)
            videoDataOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as NSString:Int(kCVPixelFormatType_32BGRA)]

            videoDataOutput.alwaysDiscardsLateVideoFrames = true
            session.addOutput(videoDataOutput)
        }
    }

    // AVCaptureVideoDataOutputSampleBufferDelegate
    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
        if let buffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
            process(pixelBuffer: buffer)
        }
    }
    func process(pixelBuffer: CVPixelBuffer) {
        let sourceRowBytes = CVPixelBufferGetBytesPerRow( pixelBuffer );
        let width = CVPixelBufferGetWidth( pixelBuffer );
        let height = CVPixelBufferGetHeight( pixelBuffer );

        let rt = CVPixelBufferLockBaseAddress( pixelBuffer, .readOnly );
        if (rt == kCVReturnSuccess) {
            ... 
            Do your processing of the pixeldata here
            ...
            CVPixelBufferUnlockBaseAddress(pixelBuffer, .readOnly)
        }
    }

    private let session = AVCaptureSession()
    private let sessionQueue = DispatchQueue(label: "session queue", attributes: [], target: nil) // Communicate with the session     
    private let videoDataOutput = AVCaptureVideoDataOutput()
}