pbmtopgm
converts PBM bitmap to PGM grayscale by averaging pixel regions
TLDR
Convert bitmap to grayscale
$ pbmtopgm [width] [height] [input.pbm] > [output.pgm]
SYNOPSIS
pbmtopgm width height [file]
DESCRIPTION
pbmtopgm converts PBM bitmap to PGM grayscale by averaging pixel regions. Anti-aliases bitmap edges. Part of Netpbm toolkit.
PARAMETERS
width
Averaging width.height
Averaging height.