/usr/bin/tiff2bw: invalid option -- '-'
LIBTIFF, Version 4.7.2
Copyright (c) 1988-1996 Sam Leffler
Copyright (c) 1991-1996 Silicon Graphics, Inc.

Convert a color TIFF image to greyscale

usage: tiff2bw [options] input.tif output.tif
where options are:
 -R %		use #% from red channel
 -G %		use #% from green channel
 -B %		use #% from blue channel

 -r #		make each strip have no more than # rows

 -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
 -c g4		compress output with CCITT Group 4 encoding
 -c none	use no compression algorithm on output