XImaging is a lightweight, multithreaded, open source image viewer for
FreeBSD, Linux and other Unix like platforms running X11. The
application can be run in viewer or browser mode. The viewer displays
full size images and provides zooming, panning, rotation and other
useful functions. The browser searches a directory for known image file
types and displays them as thumbnails. Additionally both modes provide
basic file management routines. A custom tool may be specified for
opening selected files in another application for editing.

It is written in C, and uses the Motif widget toolkit. The source code
may be modified and distributed under the terms of the X/MIT license.