Convert gbr to pnm Online: gbr2pnm

You can use Tom's Editor to easily convert images from
GIMP Brush .GBR to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

GBR

GBR are images that can be used as brushes in GIMP image editor.

PNM

PNM images are uncompressed 24 bit RGB images. Can cannot store Alpha channel. PNM images come in 2 types: binary and text. Especially popular on Linux.