With the use of layers and clipping masks in Pixelmator, you can precisely control how images are composited. Learn how to make detailed corrections to your images and combine multiple layers together in this tutorial.

http://www.youtube.com/watch?v=xFFdAst72xM

This tutorial is a single movie from the Up and Running with Pixelmator course by lynda.com author Rich Harrington. The complete course is 3 hours and 33 minutes and shows how to get up and running with Pixelmator, a full-featured image-editing tool for the Mac.