tgd reads text files and writes GIF files. Typically, in a Unix
environment, it would be at the end of a pipe: my_program | tgd. It
can also be invoked on a file: tgd my_text_file. By using the special
file handle stdout, it can be used in WWW applications to push images
to a browser. It was born out of a desire to learn the gd graphics
library and Perl simultaneously (but it can be used with any scripting
language). 

WWW: http://dendrome.ucdavis.edu/tgd/tgd.html