Aspect Fill and Aspect Fit calculations in Swift

CGSize+AspectFunctions.swift

// port of http://stackoverflow.com/a/17948778/3071224

import UIKit
import Foundation

extension CGSize {
    static func aspectFit(aspectRatio : CGSize, var boundingSize: CGSize) -> CGSize {
        let mW = boundingSize.width / aspectRatio.width;
        let mH = boundingSize.height / aspectRatio.height;

        if( mH < mW ) {
            boundingSize.width = boundingSize.height / aspectRatio.height * aspectRatio.width;
        }
        else if( mW < mH ) {
            boundingSize.height = boundingSize.width / aspectRatio.width * aspectRatio.height;
        }
        
        return boundingSize;
    }
    
    static func aspectFill(aspectRatio :CGSize, var minimumSize: CGSize) -> CGSize {
        let mW = minimumSize.width / aspectRatio.width;
        let mH = minimumSize.height / aspectRatio.height;

        if( mH > mW ) {
            minimumSize.width = minimumSize.height / aspectRatio.height * aspectRatio.width;
        }
        else if( mW > mH ) {
            minimumSize.height = minimumSize.width / aspectRatio.width * aspectRatio.height;
        }
        
        return minimumSize;
    }
}

Example.swift

// to determine the calculated size of a UIImage
let sizeBeingScaledTo = CGSizeAspectFit(myImage.size, myImageView.frame.size);