Modify pixels of a UIImage

applyfilter.swift

func applyFilter(to image: UIImage) -> UIImage? {
  guard let context = prepareContext(for: image),
	let pixelBuffer = getPixelBuffer(from: context) else {
	return nil
  }

  // TODO: Hier müssen wir die einzelnen Pixel im pixelBuffer modifizieren und wieder
  // zurück in den pixelBuffer schreiben.
	
  guard let outputCGImage = context.makeImage() else {
    return nil
  }
  return UIImage(cgImage: outputCGImage, scale: image.scale, orientation: image.imageOrientation)
}