An archive of Robert Bradford's mktartan program, compiled from its scattered remains on the net. Mostly recovered from archive.org — https://web.archive.org/web/20080515061850/http://www.holestone.net/tartan/mktartan.html — and that page provides usage instructions
cc -o mktartan mktartan.c
mktartan -c -s2 -x tdf/Mitchell.tdf
Samples folder contains PNG files converted from xpm files using the example setting above.
From the source:
/* # Builds XPM or BMP files from a TDF tartan definition file. # Copyright (c) 1998 Robert Bradford. All Rights Reserved. # # This software may be freely used for any purpose whatsoever, # provided the copyright message is left intact. # # Have fun. */