Whetther you use Windows, Mac, or Linux, a free and open-source alternative to PhotoShop is GIMP. I love using GIMP and teaching others the basics of how to use it. You can find my GIMP page with links to resources and download at http://www.charlesaelliott.com/tutorials/gimp/.
This tutorial is from Bernhard Stockmann at GIMPusers.com…
Tutorial: Create a colored zig zag pattern!
via Create a colored zig zag pattern! — Tutorials — gimpusers.com.