lvlpf(3)

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

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

INPUT

    1. image -- xvimage structure
    2. order -- low-pass filter order;
                default value is 1
    3. type -- low-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.

MODIFICATIONS
Marcelo Teran, Ramiro Jordan
18-Nov-90 Scott Wilson Changed cutoff to float from int!

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

DESCRIPTION
lvlpf performs a low-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
vlpf(1), intro(3), vipl(3), verror(3), vutils(3)

RESTRICTIONS
lvlpf will complain if asked to operate on non-COMPLEX data storage type 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.