Convert gg to pnm Online: gg2pnm

You can use Tom's Editor to easily convert images from
Koala Painter 2, packed .GG to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

GG

Koala Painter is a Commodore 64 program do edit images. GG images are packed using RLE compression.

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.