gphoto2 - Add digital camera support
gpm - Add support for sys-libs/gpm (Console-based mouse driver)
gps - Add support for Global Positioning System
-graphicsmagick - Enable support for the GraphicsMagick image converter (fork of media-gfx/imagemagick)
+graphicsmagick - Build and link against GraphicsMagick instead of ImageMagick (might require USE=imagemagick if optional)
graphviz - Add support for the Graphviz library
gsl - Use the GNU scientific library for calculations
gsm - Add support for the gsm lossy speech compression codec
icu - Enable ICU (Internationalization Components for Unicode) support, using dev-libs/icu
idn - Enable support for Internationalized Domain Names
ieee1394 - Enable FireWire/iLink IEEE1394 support (dv, camera, ...)
-imagemagick - Enable support for the ImageMagick image converter
+imagemagick - Enable optional support for the ImageMagick or GraphicsMagick image converter
imap - Add support for IMAP (Internet Mail Application Protocol)
imlib - Add support for imlib, an image loading and rendering library
infiniband - Enable Infiniband RDMA transport support