BWFILTER(1)

NAME
bwfilter - apply a 3x3 filter to a black and white bw file

SYNOPSIS

bwfilter [-f type] [-v] [-d div] [-O offset] [-s squaresize] [-w width] [-n height] [-o out_file] [file.bw] > newfile.bw

DESCRIPTION

bwfilter applies one of several 3x3 kernel filters to a black and white bw(5) format file. It will take a file name or else read from standard input. The input file size will be assumed to be 512x512 pixels unless the -s, -w, or -n flags are used to tell it otherwise (see brlcad(1)). By default a low pass filter is used. The -f type flag can be used to specify a different type of filter.

The type choices include:

lo
    low pass, the default.

hi
    high pass

vg
    vertical gradient

hg
    horizontal gradient

la
    laplacian

b
    boxcar low pass

Most filters divide the result of the kernel multiplication by some value about in order to scale it back to a 0->255 range. For example, the boxcar divides by nine. The -d flag can be used to change this divisor. Some filters also add an offset to their results. The output of a laplacian for example is "centered" about zero, thus it adds 128 to the answer to yield a difference from neutral grey. The -O flag can be used to change this offset.

The -v flag displays the max and minimum values and the kernel information on standard error.

BUGS

This should allow any 3x3 kernel to be specified.

SEE ALSO

brlcad(1), bwscale(1), bw(5)

AUTHOR

BRL-CAD Team

COPYRIGHT

This software is Copyright (c) 1989-2021 by the United States Government as represented by U.S. Army Research Laboratory.

BUG REPORTS

Reports of bugs or problems should be submitted via electronic mail to devs@brlcad.org