Invert a UIImage at runtime using Core Image CIFilter + CIContext

UIImage+Invert.swift

extension UIImage {
    func invertedImage() -> UIImage? {
        
        let img = CoreImage.CIImage(CGImage: self.CGImage)
        
        let filter = CIFilter(name: "CIColorInvert")
        filter.setDefaults()
        
        filter.setValue(img, forKey: "inputImage")
        
        let context = CIContext(options:nil)
        
        let cgimg = context.createCGImage(filter.outputImage, fromRect: filter.outputImage.extent())

        return UIImage(CGImage: cgimg)
    }
}