vinverse(1)

PROGRAM
vinverse - Perform image restoration by inverse filtering in the frequency domain.

SYNTAX

vinverse

-i1 FFT of image to be restored

-i2 FFT of PSF function

-o1 FFT of restored image

-t  minimum PSF threshold

[-i3]
    FFT of reference image

[-o2]
    FFT of effective PSF funtion

[-V]
    Gives the version for vinverse

[-U]
    Gives the usage for vinverse

[-P]
    Prompts for command line options

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

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

DESCRIPTION
vinverse performs restoration of images in the spatial domain by inverse 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 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 reffile (reference image) is an image which, if supplied, is subtracted from the input image before the inverse filter is applied. This is handy for removing some constant background from the image before the restoration is done.

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

The effPSFfile (effective PSF function) 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

OPTIONAL ARGUMENTS

-i3 type: infile
    desc: FFT of reference image

-o2 type: outfile
    desc: FFT of effective PSF funtion

EXAMPLES
vinverse -i1 fft_img1 -i2 fft_psf_img -t 10 -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.

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

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

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