DOKK / manpages / debian 10 / netpbm / g3topbm.1.en
g3topbm(1) General Commands Manual g3topbm(1)

g3topbm - convert a Group 3 fax file into a portable bitmap

g3topbm [-kludge] [-reversebits] [-stretch] [g3file]

Reads a Group 3 fax file as input. Produces a portable bitmap as output.

Tells g3topbm to ignore the first few lines of the file; sometimes fax files have some junk at the beginning.
Tells g3topbm to interpret bits least-significant first, instead of the default most-significant first. Apparently some fax modems do it one way and others do it the other way. If you get a whole bunch of "bad code word" messages, try using this flag.
Tells g3topbm to stretch the image vertically by duplicating each row. This is for the low-quality transmission mode.

All flags can be abbreviated to their shortest unique prefix.

The standard for Group 3 fax is defined in CCITT Recommendation T.4.

Probably.

pbmtog3(1), pbm(5)

Copyright (C) 1989 by Paul Haeberli <paul@manray.sgi.com>.

02 October 1989