PHP5-GD and X11 requirement

[Roop Nanuwa]

I'm trying to add GD support into my PHP5 install and I'm utterly
confused by one thing. For some reason, GD has a dependency on X. Why
is that? This is a server  that doesn't even have a monitor plugged
in, what features of X does the PHP GD module require? It seems rather
ridiculous to me that there would that requirement.

What's the reasoning behind it? What features of the X libraries does
GD make use of?