scalecrop.swift

import UIKit

// Swift rewrite challenge
// Starting point: https://gist.github.com/jkereako/200342b66b5416fd715a#file-scale-and-crop-image-swift


extension CGSize {
    func scale(toSize newSize: CGSize, fit: Bool) -> CGSize {
        let test : (CGFloat,CGFloat) -> CGFloat = fit ? { max($0, $1) } : { min($0, $1) }
        let scale : CGFloat = test(width / newSize.width, height / newSize.height)
        return CGSize(width: (width / scale), height: (height / scale))
    }
}

extension UIImage {
    
    func scale(toSize newSize:CGSize, fit:Bool) -> UIImage {
        
        guard size != newSize else { return self }
        
        let scaledSize = size.scale(toSize: newSize, fit: fit)
        let drawingOrigin = CGPoint(x: (newSize.width - scaledSize.width) / 2.0,y: (newSize.height - scaledSize.height) / 2.0)
        
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
        defer { UIGraphicsEndImageContext() }
        
        UIColor.blackColor().setFill()
        UIRectFill(CGRect(origin: .zero, size: newSize))
        drawInRect(CGRect(origin: drawingOrigin, size: scaledSize))
        
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

// Test with some basic placeholder data
guard let url = NSURL(string: "http://placehold.it/300x150") else { fatalError("Bad URL") }
guard let data = NSData(contentsOfURL: url) else { fatalError("Bad data") }
guard let img = UIImage(data: data) else { fatalError("Bad data") }

let outImageFit = img.scale(toSize: CGSize(width: 200, height: 200), fit: true)
let outImageFill = img.scale(toSize: CGSize(width: 200, height: 200), fit: false)