Convert hgb to pnm Online: hgb2pnm
You can use Tom's Editor to easily convert images from
HinterGrundBild .HGB to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.
Go to Tom's Editor
HinterGrundBild is an image format with extension HGB.
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.