pbmtopgm

Convert a PBM image to PGM by averaging areas surrounding individual pixels. See also: pnmconvol, pamditherbw. More information: https://netpbm.sourceforge.net/doc/pbmtopgm.html.

• Convert PBM image to PGM by averaging the wxh-sized area surrounding each pixel:

pbmtopgm w h path/to/image.pbm > path/to/output.pgm