Correctly scaling a full size background image in iOS, to seamlessly transition from launch image

LoginViewController.swift

override func viewDidLoad() {
    super.viewDidLoad()

    self.view.backgroundColor = UIColor.whiteColor()
    
    let screenSize: CGRect = UIScreen.mainScreen().bounds
    
    var bgImage = UIImageView(image: UIImage(named: "login-bg"))
    bgImage.center = CGPointMake(self.view.bounds.size.width / 2, self.view.bounds.size.height / 2)
    bgImage.transform = CGAffineTransformMakeScale(screenSize.width / 414, screenSize.height / 736)
    
    self.view.addSubview(bgImage)
}