GAMGI uses the file extension to automatically determine the file format. 
To export a standard .jpeg file of the whole graphic area of a GAMGI window, 
just give the filename the extension 
.jpeg or 
.jpg.
The command line application 
pnmtojpeg, widely available and 
usually installed by default in most Linux distributions, must be 
installed, otherwise GAMGI will be unable to export a jpeg file.
This a loss infomation format, not particularly recommended, 
particularly when rendering wired objects such as cells and text.
Currently the quality parameter is set to 
75% (the pnmtojpeg default).