Camera feed of dimensions one pixel by one pixel - swift

Question

This is a rather strange request, but I am looking to build an app that has a live camera feed taking up the whole screen. However, instead of displaying the normal resolution it would all be one color. In particular, I want to take the color of what normally would be the middle pixel on the screen and make that take up the entire screen. It needs to be done live and fast.
I attempted to make a function which saved the capturesession as a uiimage and then got the pixel data from that, however, it proved to be slow in real time. Any suggestions?

Answer 1

Assuming you have an AVCaptureSession setup. You need to setup a AVCaptureVideoDataOutput and then setup its sample buffer delegate. The delegate class should override func captureOutput(AVCaptureOutput!, CMSampleBuffer!, AVCaptureConnection!). Within this function you can get access to the pixel buffer to sample your centre point. You could do it as below. I've left the actual sampling of the centre point to you.
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()
}