http://www.theregister.co.uk/2008/10/14/mac_secrets_imagekit_internals/
Mac Secrets When Leopard arrived, a number of significant new technologies came with it, including Objective-C 2.0, Core Animation, and ImageKit.
ImageKit brings together a number of classes designed to make it easy to display and edit images, view slideshows, take pictures using an attached or built-in camera, and more besides. In fact, ImageKit is itself built on top of Core Animation, hence the snazzy effects that it uses. The latest version of Preview also makes use of ImageKit when displaying and manipulating images.
This all sounds great and doubtless gets you straining at the leash to start working with the ImageKit classes, right? Unfortunately, there are some intriguing holes in the documentation. These piqued my interest.
The IKImageView class is designed (as the name suggests) to implement image viewing along with simple editing capabilities. It's easy to configure an instance of this class so that double-clicking the image view brings up a standard edit panel, from where the user can adjust things like gamma, saturation and brightness, as well as applying assorted Core Image filters.