NAME

     Ideal_Band_Pass - perform ideal bandpass filtering

SYNOPSIS

      #include <math.h>
      #include <stdio.h>
      #include <stdlib.h>
      #include "CVIPdef.h"
      #include "CVIPimage.h"

     Image  *Ideal_Band_Pass(Image  *in_Image,int  block_size,int
     dc,int inner,int  outer)

      <in_Image> - pointer to an Image structure
      <block_size> - desired block size
      <dc> - drop(0) or retain(1) dc component
      <inner> - inner cutoff frequency
      <outer> - outer cutoff frequency

PATH

     $CVIPHOME/XFORMFILTER/filter.c

DESCRIPTION

     Ideal_Band_Pass() performs  two-dimensional  ideal  bandpass
     filtering in transform domain on input image.  All frequency
     components that are in the band enclosed by the  circle  (or
     1/4  circle if dc component is on the upper left-hand corner
     of its transform plane) with radius  inner  and  the  circle
     with  radius  outer  will be passed with no attenuation. All
     frequencies outside the circular band (or 1/4 circular band)
     are  completely attenuated. If dc equals 1, the dc component
     will be retained, if dc equals 0, it will be dropped

TYPES AND CONSTANTS

     None

RETURN VALUES

     A filtered image

HISTORY

     History information recorded: None

DIAGNOSTICS

      The Ideal_Band_Pass 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  cutoff  frequencies can range from 1 to blocksize/2 and
     the Ideal_Band_Pass 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_Band_Pass()
     with filtertype=5.  The cutoff frequencies 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
     bpf_setup()  is  to  be  used to call Ideal_Band_Pass(), the
     transform must be setup and recognized by bpf_setup(),  oth-
     erwise   the   setup   program   automatically  assumes  the
     transform's dc component is on the center (dcpos=1).

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 band pass
      filtering on the transformed image with the lower cut off
      equal to 0 and the higher cut off equal to 64 */
      cvipImage = (Image *)Ideal_Band_Pass(cvipImage,256,1,0,64);
      /* 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.