MyPaint is a fast and easy open-source graphics application for digital painters. It lets you focus on the art instead of the program. You work on your canvas with minimum distractions, bringing up the interface only when you need it. MyPaint runs on GNU/Linux as well as Windows
Instead of explaining all the cool features and power of MyPaint lets just look at some screenshots and finished paintings.
This is a screenshot of MyPaint running in Ubuntu 11
This screenshot is taken in an older version of Linux
Screenshot of adjusting some brush settings in MyPaint
Another screenshot taken in Linux
Instead of listing the technical aspects of MyPaint let's look at some finished paintings. These are found at deviantart http://mypaint.deviantart.com/gallery/.
For Windows users MyPaint is available at MyPaint, there are also extra brushes and a gimp plugin for download. There is a tutorial for people who've never used MyPaint, Basic Usage Tutorial. After going through the basic usage tutorial check out the wiki to learn more advanced tricks MyPaint Wiki.
See MyPaint in action with a timelapse. This was posted in 2009.
Kristen Stewart, portrait in MyPaint approximately 1 hour into lees than 10 min