GIMP is free online. It is comparable to Photoshop...same type of platform. If easy is what you're looking for, then go with Photoscape. Both can be downloaded online.
photofiltre is a very good free download program,, I use it all the time for editing, and i edit pretty much everything.... http://photofiltre.en.softonic.com/
http://photofiltre.en.softonic.com/