
vbpf(1)                      Khoros                       vbpf(1)

PROGRAM
     vbpf - Perform Band-pass filtering on an  image in the fre-
     quency domain.

SYNTAX
     vbpf

     -i             input image filename

     -o             output image filename

     -n             order of filter used

     -c             Cutoff frequency radius

     -w             bandwidth of filter

     [-V]           Gives the version for vbpf

     [-U]           Gives the usage for vbpf

     [-P]           Prompts for command line options

     [-A [file1]]   Creates the answer file called vbpf.ans or
                    file1

     [-a [file1]]   Uses vbpf.ans or file1 as the answer file

DESCRIPTION
     vbpf performs a band-pass filtering operation on an image in
     the frequency domain.  The filter used is a Butterworth
     radially symmetric band-pass filter. The filter cutoff is a
     radius normalized to the longest image dimension (lets you
     filter non-square images, but with an elliptical cutoff
     area). The order of the filter is an integer specifying the
     sharpness of the cutoff. The band width must also be speci-
     fied, and is in terms of pixels.

     The cutoff frequency is determined by taking 1/2 the length
     of the longest side of an image and normalizing that to 1.
     The cutoff frequency is then some value between 0 and 1.
     Example: take a 256x256 image, divide by 2 = 128, normalize
     to 1 and determine the cutoff frequency, A 0.25 cutoff would
     correspond to a cutoff at pixel location row or column 160.

REQUIRED ARGUMENTS
     -i     type: infile
            desc: input image filename

     -o     type: outfile
            desc: output image filename

     -n     type: integer
            desc: order of filter used

     -c     type: float
            desc: Cutoff frequency radius

     -w     type: integer
            desc: bandwidth of filter

OPTIONAL ARGUMENTS
     none

EXAMPLES
     vbpf -i input.image -o output.image -n 1 -c .1 -w 1000

     This command band-pass filters input.image and stores the
     result in output.image.  The filter is of order 1 and the
     cutoff radius is .1.  The bandwidth is 1000.

SEE ALSO
     intro(1), verror(3), vgparms(3), vutils(3), lvbpf(3)

RESTRICTIONS
     vbpf will complain if asked to operate on data storage types
     other than COMPLEX input images.

     Filters of high order can take a long time to do their work.

COPYRIGHT
     Copyright 1991, University of New Mexico.  All rights
     reserved.

Khoros                    Release: 1.0                          1

