AzPainter is a full color painting application for Unix-like systems for
illustration drawing.  It is not suitable for "dot editing" or pixel-art.
Since the color is handled internally with 16-bit precision (15-bit fixed
point), color accuracy is increased at the expense of more memory usage.

It provides considerable subset of functionality offered by GIMP and even
Adobe Photoshop (particularly, has one of the best support for its native
PSD format among FOSS) while being very lightweight and blazingly fast.

WWW: http://azsky2.html.xdomain.jp/soft/azpainter.html