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] [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 bw used to change this offset.

The -v flag displays the kernel values 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) 1989-2013 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>.