iOS Alternate Icon not changing

I have followed few tutorials on setting alternative icons in iOS but I cannot get it to work properly. The important part in my Info.plist looks like this:

<key>CFBundleIcons</key>
<dict>
    <key>CFBundlePrimaryIcon</key>
    <dict>
        <key>CFBundleIconFiles</key>
        <array>
            <string>default</string>
        </array>
        <key>UIPrerenderedIcon</key>
        <false/>
    </dict>
    <key>CFBundleAlternateIcons</key>
    <dict>
        <key>six</key>
        <dict>
            <key>CFBundleIconFiles</key>
            <array>
                <string>six</string>
            </array>
            <key>UIPrerenderedIcon</key>
            <false/>
        </dict>
        <key>crazy</key>
        <dict>
            <key>CFBundleIconFiles</key>
            <array>
                <string>crazy</string>
            </array>
            <key>UIPrerenderedIcon</key>
            <false/>
        </dict>
    </dict>
</dict>

And the code for the view controller, very simple:

class ViewController: UIViewController {

@IBOutlet weak var segment: UISegmentedControl!

override func viewDidLoad() {
    super.viewDidLoad()
    segment.addTarget(self, action: #selector(segmentChanged(_:)), for: .valueChanged)
    // Do any additional setup after loading the view, typically from a nib.
}

@objc func segmentChanged(_ sender: UISegmentedControl) {
    var icon: String?
    switch sender.selectedSegmentIndex {
    case 1:
        icon = "six"
    case 2:
        icon = "crazy"
    default:
        icon = nil
    }
    changeIcon(icon)
}

func changeIcon(_ icon: String?) {
    if UIApplication.shared.supportsAlternateIcons {
        UIApplication.shared.setAlternateIconName(icon, completionHandler: { (error) in
            print("\(error?.localizedDescription)")
        })
    }
  }
}

When the method gets called I get prompt saying

You have changed the icon for "App".

But the icon that is displayed is the default one My icon files are named: six@2x.png, six@3x.png, crazy@2x.png, crazy@3x.png, default@2x.png, default@3x.png Why is it not changing? Are there any special steps for putting the image files in the project? I have put mine in the "res" folder

Project: https://www.dropbox.com/s/nboslz2s6gagvwl/AltIcon.zip?dl=0

Turns out it was problem with the software I was using to scale down images, it wasn't saving PNG files properly.