pnmscale - scale a PNM image
pnmscale [ scale_factor | -xysize cols rows | -reduce reduction_factor | [-xsize=cols | -width=cols | -xscale=factor] [-ysize=rows | -height=rows | -yscale=factor] | -pixels n ] [-verbose] [-nomix] [pnmfile]
This program is part of Netpbm(1).
pnmscale was obsoleted by pamscale(1),introducedwithNetpbm10.20 (January 2004). pamscale is backward compatible with pnmscale, plus adds many additional functions, including the ability to process PAM images, and tends to produce better results.
pnmscale remains in the current Netpbm package because it probably has fewer bugs for now than pamscale, and may have superior performance characteristics in some cases. Some day, pnmscale will probably become an alias for pamscale.
You can use the pamscale documentation for pnmscale, considering the following differences: