GraphicsMagick-devel contains the static libraries and header files you'll
need to develop GraphicsMagick applications using the Magick++ C++ bindings.
GraphicsMagick is an image manipulation program.
If you want to create applications that will use Magick++ code
or APIs, you'll need to install GraphicsMagick-c++-devel, ImageMagick-devel and
GraphicsMagick.
You don't need to install it if you just want to use GraphicsMagick, or if you
want to develop/compile applications using the GraphicsMagick C interface,
however.