To run the GD library you need to recompile Apache using WHM.
•From your WHM, go to Software -> EasyApache
•Start your customization based on your current profile
•look for "IonCube Loader for PHP" in the second page and Check it.
•When you get to "Step 5" click the option "Exhaustive Options"
•check the checkbox for GD under PHP
•Go ahead with the process for Build & Compile