Convert pnm to gg Online: pnm2gg
You can use Tom's Editor to easily convert images from
Portable aNy Map .PNM to Koala Painter 2, packed
Tom's Editor is a free, online image manipulation and converter program.
Go to Tom's Editor
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.
Koala Painter is a Commodore 64 program do edit images. GG images are packed using RLE compression.