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.