vwiener(1)

PROGRAM
vwiener - Perform image restoration by Wiener (least-squares) filtering.

SYNTAX

vwiener

-i1 FFT of image to be restored

-i2 FFT of PSF function

-o1 FFT of restored image

-t  minimum PSF threshold

-w  Weiner parameter

[-i3]
    FFT of reference image

[-o2]
    FFT of restoration filter

[-V]
    Gives the version for vwiener

[-U]
    Gives the usage for vwiener

[-P]
    Prompts for command line options

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

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

DESCRIPTION
vwienevwiener performs restoration of images in the spatial domain by Wiener filtering in the frequency domain. The idea is to deconvolve the blurring function from the blurred image. A few problems exist in performing this operation, as described in great detail in any good image processing book. The Wiener filter performs better than the inverse filter when noise is present in the data.

The major difficulty lies in how small the denominator is allowed to be before you call it garbage. The value chosen is supplied as the -t thresh value. Ideally, this will be just above the noise floor in the image, but experimentation is the best guide here.

The restoration parameter controls how smoothly the modified PSF blends into the flat cutoff regions generated by the thresholding operation. For more information, see Rosenfeld & Kak, page 287.

The reffile is an image which, if supplied, is subtracted from the input image before the weiner filter is applied. This is handy for removing some constant background from the image before the restoration is done.

The PSFfile is the transform of the Point-Spread Function, or blurring function that is to be deconvolved from the input image.

The effPSFfile is the same as the PSFfile after the thresholding operation has been applied. Taking the inverse Fourier transform of this file gives the effective PSF as used in the restoration. The idea is that is should be reasonably close to the real PSF.

REQUIRED ARGUMENTS

-i1 type: infile
    desc: FFT of image to be restored

-i2 type: infile
    desc: FFT of PSF function

-o1 type: outfile
    desc: FFT of restored image

-t  type: float
    desc: minimum PSF threshold

-w  type: float
    desc: Weiner parameter

OPTIONAL ARGUMENTS

-i3 type: infile
    desc: FFT of reference image

-o2 type: outfile
    desc: FFT of restoration filter

EXAMPLES
vwiener -i1 fft_img1 -i2 fft_psf_img -t 10 -w 5 -o1 fft_out_img

This command deconvolves the second input image from the first. Fft_img1 is the fft of the image to deconvolve from, and fft_psf_img is the fft of the PSF function of the image to deconvolve. The threshold for the denominator is 10, and the resulting fft image is fft_out_img. The Wiener parameter is 5.

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

RESTRICTIONS
all input images must be the same data storage type (VFF_TYP_COMPLEX) and size.

COPYRIGHT
Copyright 1992, University of New Mexico. All rights reserved.