Spencer Thomas said about the original TCL GD: 

	Thomas  Boutell's Gd  package  provides a  convenient way  to
	generate PNG images with a C program. If you, like me, prefer
	Tcl for CGI applications, you'll want my TCL GD extension.

The software  is now maintained  by John Ellson  <ellson@lucent.com>, it
seems.

WWW:	http://graphviz.org/cgi-bin/man?gdtclft