ZBar is an open source software suite for reading bar codes from various
sources, such as video streams, image files and raw intensity sensors. It
supports many popular symbologies (types of bar codes) including EAN-13/UPC-A,
UPC-E, EAN-8, Code 128, Code 39, Interleaved 2 of 5 and QR Code.

The flexible, layered implementation facilitates bar code scanning and decoding
for any application: use it stand-alone with the included GUI and command line
programs, easily integrate a bar code scanning widget into your Qt, GTK+ or
PyGTK GUI application, leverage one of the script or programming interfaces
(Python, Perl, C++) ...all the way down to a streamlined C library suitable for
embedded use.