Before you start compiling libgd you'll need to 'yum-install' devel packages for png, jpeg, freetype and fontconfig. Once you've done this you can download the source package of libgd http://www.libgd.org/releases/gd-2.0.35.tar.gz and do the typical:
$ ./configure --with-jpeg --with-png --with-freetype
$ make
$ sudo make install
You might want to add the library location (default /usr/local/lib) to /etc/ld.so.conf.d and add /usr/local/bin to your PATH variable.
Now you're almost ready to build gnuplot after you've downloaded the source package http://sourceforge.net/projects/gnuplot/files/gnuplot/4.4.2/gnuplot-4.4.2.tar.gz/download. However, there is a problem with the libgd-config tool that is used by gnuplot's configure. It prints out a bogus library in the libs sections:
$ gdlib-config --all
GD library 2.0.35
includedir: /usr/local/include
cflags: -I/usr/local/include
ldflags: -L/usr/lib64 -L/usr/lib64
libs: -lXpm -lX11 -ljpeg -lfontconfig -lfreetype -lpng12 -lz -lm @LIBICONV@
libdir: /usr/local/lib
features: GD_XPM GD_JPEG GD_FONTCONFIG GD_FREETYPE GD_PNG GD_GIF GD_GIFANIM GD_OPENPOLYGON
In order to dynamically get rid of the @LIBICONV@ entry I renamed gdlib-config and created tiny shell script that removes the bogus library from the output:
$ mv /usr/local/bin/gdlib-config /usr/local/bin/gdlib-config-org
$ cat /usr/loca/bin/gdlib-config
#!/bin/bash
/usr/local/bin/gdlib-config-org $* | sed "s/@LIBICONV@//"
Now glib-config produces the correct output and you can configure and make install gnuplot:
$ ./configure --with-gd=/usr/local/lib
$ make
$ sudo make install
Without patching gdlib-config gnuplot's configure will disable PNG and TTF support by default.
