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 mutiplication 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).

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