A UIView subclass for interactively comparing two separate images
Add .h and .m to your Xcode project. Either instantiate and add to your view heirarchy or drop a UIView into interface builder and set its class to SplitImageView.
Either assign the left and right images at runtime or use the IBDesignable to type the names into the inspector in interface builder.
Drag the slidey thing to compare your two separate images at runtime.