Ill have to go with Paint.NET for photo editing, etc. Its like Photoshop except better. Heres the website: http://www.eecs.wsu.edu/paint.net/
Its legally free, and it has this code lab plugin that if you know C+ you can make any effect imaginable . Id advise on downloading the beta or alpha version. Dont worry, it doesnt crash. It has more features or something than the other non-beta/alpha version.