NAME
Ideal_High - perform ideal highpass filtering
SYNOPSIS
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "CVIPdef.h"
#include "CVIPimage.h"
Image *Ideal_High(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_High() performs two-dimensional ideal highpass filter-
ing 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 filtered, while all frequen-
cies outside the circle (or 1/4 circle) are left completely
intact. If dc equals 1, the dc component will be retained,
if it equals 0, it 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);
print_CVIP("0Enter 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 high pass
filtering on the transformed image with the cut off
frequency equal to 64 */
cvipImage = (Image *)Ideal_High(cvipImage,256,1,64);
/* the following call performs the inverse fft_transform
in the filtered image with the block size equal to 256 */
filtered image with the block size equal to 256 */
cvipImage = (Image *)ifft_transform(cvipImage,256);
print_CVIP("0Enter the Output File Name: ");
outputfile = getString_CVIP();
view_Image(cvipImage,outputfile);
write_Image(cvipImage,outputfile,CVIP_NO,CVIP_NO,format,1);
free(outputfile);
}
DIAGNOSTICS
The Ideal_High filter will work for both real-valued and
imaginary-valued transform. If the origin of the transform
is on the center of its frequency plane (shifted), the cut-
off frequency can range from 1 to blocksize/2 and the
Ideal_High function can be called directly with correct
parameters. If the origin of the transform is on the upper
left-hand corner of its frequency plane,
nonfft_xformfilter() must be used to call Ideal_High() with
filtertype=3. The cutoff frequency in this case can range
from 1 to blocksize since a block is treated as a quarter of
a regular block with its origin on the center. If
hpf_setup() is to be used to call Ideal_High(), the
transform must be setup and recognized by hpf_setup(), oth-
erwise the setup program automatically assumes the
transform's dc component is on the center (dcpos=1).
SEE ALSO
libxformfilter
AUTHOR
Copyright (C) 1996 SIUE - by Scott E. Umbaugh and Simon Low.