lvhpf(3)

LIBRARY ROUTINE
lvhpf - Perform a high-pass filtering operation on an image in the frequency domain.

LIBRARY CALL
#include "vinclude.h"
int
lvhpf(image,order,filtyp,fcut)
struct xvimage *image;
int  order,filtyp;
float fcut;

INPUT

    1. image -- xvimage structure
    2. order -- high-pass filter order;
    3. filtyp -- high-pass filter type; if 0
                 selects an exponential
                 filter (default), if 1
                 selects a butterworth filter
    4. fcut -- cutoff frequency radius;
               default value is 0.5

OUTPUT

    1. image -- holds the result of the
                high-pass filtered image.
    image is used for both the input xvimage structure and the output result xvimage structure. This is done to save space, but you must be careful not to overwrite important data.

    lvhpf returns 1 upon success and 0 on failure.

MODIFICATIONS
Marcelo Teran, Ramiro Jordan

Scott Wilson - 27-Jan-91 - Removed FFT processing code

DESCRIPTION
lvhpf performs a high-pass filtering operation on an image in the frequency domain. 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.

SEE ALSO
vhpf(1), intro(3), vipl(3), verror(3), vutils(3)

RESTRICTIONS
lvhpf will complain if asked to operate on non-COMPLEX input images.

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

AUTHOR
Scott Wilson

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