Usage:

reading a single char per line txt file
.\ttf2txf -o revenant.txf -s 10 -w 128 -h 128 -f chars.txt revenant.TTF

or, defining the chars on the command line

CHARS=0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@#$%^&*()-_=+[]{}|;:,.<>~"/?
./ttf2txf -o sans10.txf -s 10 -w 128 -h 128 -c $CHARS ARIAL.TTF