/usr/bin/tiffdither

/usr/bin/tiffdither: invalid option -- '-'
LIBTIFF, Version 4.7.2
Copyright (c) 1988-1996 Sam Leffler
Copyright (c) 1991-1996 Silicon Graphics, Inc.

Convert a greyscale image to bilevel using dithering

usage: tiffdither [options] input.tif output.tif
where options are:
 -r #      make each strip have no more than # rows
 -t #      set the threshold value for dithering (default 128)
 -f lsb2msb    force lsb-to-msb FillOrder for output
 -f msb2lsb    force msb-to-lsb FillOrder for output

 -c lzw[:opts] compress output with Lempel-Ziv & Welch encoding
    #          set predictor value
    For example, -c lzw:2 for LZW-encoded data with horizontal differencing
 -c zip[:opts] compress output with deflate encoding
    #          set predictor value
 -c packbits   compress output with packbits encoding
 -c g3[:opts]  compress output with CCITT Group 3 encoding
    Group 3 options:
    1d         use default CCITT Group 3 1D-encoding
    2d         use optional CCITT Group 3 2D-encoding
    fill       byte-align EOL codes
    For example, -c g3:2d:fill for G3-2D-encoded data with byte-aligned EOLs
 -c g4         compress output with CCITT Group 4 encoding
 -c none       use no compression algorithm on output