This program is part of Netpbm.
pgmtost4 reads a PGM image as input and produces a Santa Barbara Instrument Group SBIG ST-4 camera CCD image as output.
Note that this format is distinct from the SBIG format used with mos SBIG cameras. For that, see pgmtosbig
pgmtosbig was new in Netpbm 10.70, and was intended primarily as a test tool for sbigtopgm.