mkbitmap 1.16. Transforms images into bitmaps with scaling and filtering.

Usage: mkbitmap [options] [file...]
Options:
 -h, --help           - print this help message and exit
 -v, --version        - print version info and exit
 -l, --license        - print license info and exit
 -o, --output <file>  - output to file
 -x, --nodefaults     - turn off default options
Inversion:
 -i, --invert         - invert the input (undo 'blackboard' effect)
Highpass filtering:
 -f, --filter <n>     - apply highpass filter with radius n (default 4)
 -n, --nofilter       - no highpass filtering
 -b, --blur <n>       - apply lowpass filter with radius n (default: none)
Scaling:
 -s, --scale <n>      - scale by integer factor n (default 2)
 -1, --linear         - use linear interpolation
 -3, --cubic          - use cubic interpolation (default)
Thresholding:
 -t, --threshold <n>  - set threshold for bilevel conversion (default 0.45)
 -g, --grey           - no bilevel conversion, output a greymap

Possible input file formats are: pnm (pbm, pgm, ppm), bmp.
The default options are: -f 4 -s 2 -3 -t 0.45