Webcam video filter

We assume we have a video stream, e.g.:

let captureSession = AVCaptureSession()
captureSession.sessionPreset = AVCaptureSessionPresetPhoto

Then we add an output to the capture session:

let videoOutput = AVCaptureVideoDataOutput()
captureSession.addOutput(videoOutput)

Then we set a delegate for the videoOutput:

videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "sample buffer delegate"))

The videoOutput will call captureOutput(AVCaptureOutput!, didOutputSampleBuffer: CMSampleBuffer!, from: AVCaptureConnection!) on its delegate whenever a new buffer is received from the captureSession, i.e. a new frame from the webcam. So we start to implement that:

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

From the sample buffer, we can get a CVImageBuffer (a “pixel buffer”) with:

let pxbuf = CMSampleBufferGetImageBuffer(sampleBuffer)!

To apply a filter to this, we need to get it into the CoreImage framework, i.e. a CIImage:

let camImg = CIImage(cvImageBuffer: pxbuf)

We choose an arbitrary filter:

let comicEffect = CIFilter(name: "CIComicEffect")!

We call the filter with the CIImage as input and get a CIImage as output:

comicEffect.setValue(camImg, forKey: kCIInputImageKey)
let filteredCIImage = comicEffect.value(forKey: kCIOutputImageKey) as! CIImage!

Now we just need to repeatedly display the output CIImage.

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