Pinta is a free, open source drawing/editing program modeled after Paint.NET. Its goal is to provide users with a simple yet powerful way to draw and manipulate images on Linux, Mac, and Windows.
Use easy drawing tools to draw freehand, lines, rectangles, ellipses, and more. Use layers to help separate and group elements of your image for easy editing. Don't be afraid to experiment, Pinta tracks your full history so you can always undo.