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

A Swift 4.0 extension that returns an optional UIImage to avoid any potential crashes down the road.

import UIKit

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

To use this:

let image = UIImage(...)
let noirImage = image.noir // noirImage is an optional UIImage (UIImage?)