NAME
Ideal_Low - perform ideal lowpass filtering
SYNOPSIS
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "CVIPdef.h"
#include "CVIPimage.h"
Image *Ideal_Low(Image *in_Image,int block_size,int dc,int
cutoff)
<in_Image> - pointer to an Image structure
<block_size> - desired block size
<dc> - drop(0) or retain(1) dc component
<cutoff> - cutoff frequency
.de Ss
PATH
$CVIPHOME/XFORMFILTER/filter.c
DESCRIPTION
Ideal_Low() performs two-dimensional ideal lowpass filtering
in transform domain on input image. All frequency com-
ponents that are inside the circle (or 1/4 circle if dc com-
ponent is on the upper-left-hand corner of its transform
plane) of radius "cutoff" are passed with no attenuation,
while all frequencies outside the circle (or 1/4 circle) are
completely attenuated. If dc equals 1, the dc component will
be retained, if dc equals 0, the dc component will be
dropped.
TYPES AND CONSTANTS
None
RETURN VALUES
A filtered image
HISTORY
History information recorded: None
EXAMPLE
#include <CVIPtoolkit.h>
#include <CVIPimage.h>
#include <CVIPdef.h>
#include <CVIPconvert.h>
#include <CVIPview.h>
#define VIEWER "picture"
#define VIDEO_APP "SunVideo &"
void main()
{
Image *cvipImage;
IMAGE_FORMAT format;
char *inputfile,*outputfile;
(void) setDisplay_Image(VIEWER, "Default");
print_CVIP("\n\t\tEnter the Input File Name: ");
inputfile =(char *) getString_CVIP();
format = getFormat_CVIP(inputfile);
cvipImage = read_Image(inputfile,1);
view_Image(cvipImage, inputfile);
free(inputfile);
/* the following call performs the fft_transform on the
input image with the block size equal to 256 */
cvipImage=(Image *)fft_transform(cvipImage,256);
/* the following call performs the ideal low pass
filtering on the transformed image with the cut off
frequency equal to 64 */
cvipImage = (Image *)Ideal_Low(cvipImage,256,1,64);
/* the following call performs the inverse fft_transform
in the filtered image with the block size equal to 256 */
cvipImage = (Image *)ifft_transform(cvipImage,256);
print_CVIP("\n\t\tEnter the Output File Name: ");
outputfile = getString_CVIP();
view_Image(cvipImage,outputfile);
write_Image(cvipImage,outputfile,CVIP_NO,CVIP_NO,format,1);
free(outputfile);
}
SEE ALSO
libxformfilter
AUTHOR
Copyright (C) 1996 SIUE - by Scott E. Umbaugh and Simon Low.