CCComparatorView is a class that extends the UIImageView class.
It is created to compare the way the view is looking with an image. This is created by the need to do pixel perfect screens and to adjust things exactly like it look in the image.
You just need to add the ComparatorView in your view and bring it to front. To set the image you can just do that the way you do in UIImageView
To increase the alpha you just need to pan up with one finger. To decrease the alpha you just need to pan down with one finger.
If you pan with two finger the alpha is set to 0 and you can use your view.