UIImage+Downsample.swift

//  UIImage+Downsample.swift
//  Created by Todd Hopkinson

import UIKit

extension UIImage {
    
    func downsample(reductionAmount: Float) -> UIImage? {
        
        let image = UIKit.CIImage(image: self)
        guard let lanczosFilter = CIFilter(name: "CILanczosScaleTransform") else { return nil }
        lanczosFilter.setValue(image, forKey: kCIInputImageKey)
        lanczosFilter.setValue(NSNumber.init(float: reductionAmount), forKey: kCIInputScaleKey)

        guard let outputImage = lanczosFilter.outputImage else { return nil }
        let context = CIContext(options: [kCIContextUseSoftwareRenderer: false])
        let scaledImage = UIImage(CGImage: context.createCGImage(outputImage, fromRect: outputImage.extent))

        return scaledImage
    }
}