GD module is an interface to the GD library written by Thomas Bouttel.
"It allows your code to quickly draw images complete with lines,
arcs, text, multiple colors, cut and paste from other images, and
flood fills, and write out the result as a .PNG file. This is
particularly useful in World Wide Web applications, where .PNG is
the unencumbered format used for inline images."
It has been extended in some ways from the original GD library.
