The +Fpg / +Fng switch should result in a 16 bit grey scale image. It only
renders to 8 bit.
Adding +Fp16 / Fn16 does nothing as stated in the docs.
When rendering a gradien I only get 254 colors, instead of the 256 that
shoud be there for 8-bit.
3.8 beta on win10.
Cheers.
