pbmtoxbm
Convert a PBM image to a X11 or X10 bitmap.
TLDR
Convert a PPM image to a X11 XBM file
$ pbmtoxbm [path/to/input_file.pbm] > [path/to/output_file.xbm]
Explicitly specify whether an X11 or X10 bitmap should be generated
$ pbmtoxbm -[x11|x10] [path/to/input_file.pbm] > [path/to/output_file.xbm]