Special thanks to:

Stanislaw Kozicki, creater of cGPSmapper at http://cgpsmapper.com/,
who has made it possible for the average user to create IMG files.
cGPSmapper-created maps served as the source for this software effort. 

The Karmin project at http://karmin.sourceforge.net/.  This effort
appears to be stalled or dead, but their source code and 
documentation (while difficult to parse) was helpful.

GPSMapEdit at http://geopainting.com/, which is capable of importing
IMG files and was helpful in validating the decoding work.

MapDekode at
http://planeta.terra.com.br/informatica/download1/dekode_download.htm
by Peter Dekode.  Can read and create IMG files among other things.