Convert UIImage to grayscale keeping image quality

Question

I have this extension (found in obj-c and I converted it to Swift3) to get the same UIImage but grayscaled:

public fun         


        

Answer 1

Joe's answer as an UIImage exension for Swift 4 working correctly for different scales:

extension UIImage {
    var noir: UIImage {
        let context = CIContext(options: nil)
        let currentFilter = CIFilter(name: "CIPhotoEffectNoir")!
        currentFilter.setValue(CIImage(image: self), forKey: kCIInputImageKey)
        let output = currentFilter.outputImage!
        let cgImage = context.createCGImage(output, from: output.extent)!
        let processedImage = UIImage(cgImage: cgImage, scale: scale, orientation: imageOrientation)

        return processedImage
    }
}