bwthresh — threshold a black-and-white bw file
bwthresh reads from standard input a stream of black-and-white data in bw(5) format and thresholds it among the vals, writing the resulting bw(5) data to standard output. The vals must appear on the command line in strictly increasing order.
The grey scale 0..255 is divided evenly into n+1 bins, and each pixel of input is compared to the vals, to determine which of the n+1 grey levels should be output.
bwthresh 37 143 < file.bw > file2.bw
performs the following mapping:
if (pixel_in < 37) pixel_out = 0 else if (pixel_in < 143) pixel_out = 128 else pixel_out = 255
This software is Copyright (c) 1991-2016 by the United States Government as represented by U.S. Army Research Laboratory.