In case you haven't noticed, there are a plethora of third-party plug-ins being released for Aperture now that Apple has provided an image editing software development kit (SDK). However, if you have an idea for a plugin but don't know how to create it, it's a little hard to figure out where to begin!

First, to program for the Mac (and Aperture), you should know the C programming language. There's an excellent book, written in 1988 with plenty of used copies available, entitled C Programming Language by Kernighan and Ritchie to help you learn C. The newer book, Practical C Programming by Steve Oualline, is another great source.

Once you've learned C, it takes about two hours to learn Objective-C, which is the real language you should know to program for Aperture. The book Cocoa Programming for Mac OS X, by Aaron Hillegass ("Cocoa" is the name of the high-level framework in OS X, written in Objective-C, that provides the key controls, like windows and buttons, you need to build an application), is an excellent resource to learn Objective-C. An updated, 3rd edition, just came out in May, too! There are other excellent books, such as Learning Cocoa with Objective-C, but they are starting to show their age and frequently don't cover Objective-C 2.0. http://developer.apple.com/cocoa/ provides a useful collection of free, official content, from documentation to sample code. Two sites in particular to look at are the Introduction to the Objective-C 2.0 Programming Language and Introduction to Cocoa Fundamentals. Another good free, general resource is www.cocoadevcentral.com.

When you're up to speed on Cocoa, it's time to turn back to Aperture. Before you actually write any code, you should think about what you want your plugin to do and how the user will interact with it. Those requirements will influence what you need to figure out how to do. For example, if you want to write an exporting plugin to upload your images to a website, you will need to learn how to communicate with a server in Cocoa. But if you are writing an image editing plugin, you will probably want to learn about pixel processing instead of networking.

When ready, http://developer.apple.com/appleapplications/ is your official source for the Aperture SDK download, documentation, and sample code. Apple even has a mailing list for Aperture development at lists.apple.com. Apple engineers read and participate in that discussion, and it's a great place to get your questions answered. Aperture Plugged In, www.aperturepluggedin.com, also provides some older resources that are still useful, too!

If you're going to WWDC, make sure to attend the Extending Aperture with Image Editing Plug-Ins session on Friday from 2-3:15 (see http://developer.apple.com/wwdc/schedules/) to get an in-person walk through of how to make a plugin!