Install imgvtopgm by entering the following commands in the terminal:
sudo apt update sudo apt install imgvtopgm
Description:
PalmPilot/III Image Conversion utility
This program can convert, compress, and decompress up to 4-bit grayscale images for displaying on the PalmPilot. It can take any pbm, pnm, pgm file generated by the netpbm package and convert it into a suitable image for the Pilot. . Together with netpbm many image formats, including JPEG, PNG, GIF, TIFF and BMP, could be converted into PDB format. This can be displayed on PalmPilot/III by viewers like "ImageViewer", "TinyViewer" or "Spec".
Homepage: https://sourceforge.net/projects/imgvtopgm/
Version: 2.0-9build1
Section: universe/otherosfs