this says
To enable GD-support configure PHP --with-gd[=DIR], where DIR is the GD base install directory. To use the recommended bundled version of the GD library (which was first bundled in PHP 4.3.0), use the configure option --with-gd. GD library requires libpng and libjpeg to compile
that doesn't really mean much to me... there doesn't seem to be anywhere in the httpd.conf file that relates to GD...