iPhoto-like cropping of an image?

Question

I've been struggling over this for several days now and can't crack it. How do I achieve that neat photo cropping you see in iPhoto?

I tried using an NSImageView with a semi transparent CALayer allowing me to draw the cropping tool, but that doesn't work as the layer makes the image invisible (even though its transparency is set to 0.5).

I'm not asking for detailed code, just the global approach.

Answer 1

I found this outdated sample app from Apple which uses a subclass of NSImageView enhanced with cropping abilities. Although the project is based on PPC technology and it will not open in Xcode 4, the sources are exactly what I was looking for.