vbrf(1)

PROGRAM
vbrf - Perform Band-reject filtering on an image in the frequency domain.

SYNTAX

vbrf

-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 vbrf

[-U]
    Gives the usage for vbrf

[-P]
    Prompts for command line options

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

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

DESCRIPTION
vbrf performs a band-reject filtering operation on an image in the frequency domain. The filter used is a Butterworth radially symmetric band-reject 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 specified, 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
vbrf -i input.image -o output.image -n 1 -c .1 -w 1000

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

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

RESTRICTIONS
vbrf will complain if asked to operate on data storage type 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.