/* FFT2fltr_Low_gauss.c */
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include"mypgm.h"
#include"FFT1.h"
#include"FFT2.h"

void gaussian_lowpass_filtering( )
     /* low pass filtering */
{
  int i, j;
  double sigma;
  double factor, radius;
  
  printf("\nGaussian low pass filtering is applied to FFT coefficients.\n");
  printf("Total frequency range is 0 - %d.\n", num_of_data / 2);
  
  printf("\nEnter sdv value for Gaussian filter (ex. %d) : ", 
	 num_of_data / 16);
  scanf("%lf", &sigma);
  sigma = pow(sigma, 2);
  
  for (i = 0; i < num_of_data; i++) {
    for (j = 0; j < num_of_data; j++) {
      radius = pow(i-num_of_data/2, 2) + pow(j-num_of_data/2, 2);
      factor = exp(-radius/(2.0*sigma));
      data[i][j] *= factor;
      jdata[i][j] *= factor;
    }
  }
}


main( )
{
  load_image_data();      /* Input image load      */
  make_original_data();   /* FFT arrays generation   */
  FFT2(1);                /* 2-d FFT  */
  origin_centered_FFT();  /* FFT rearrangement */
  gaussian_lowpass_filtering();  /* Gaussian low pass filtering */
  origin_centered_FFT();  /* FFT rearrangement */
  FFT2(-1);               /* 2-d inverse FFT */
  make_output_image();    /* Image generation after IFFT */
  save_image_data();      /* Output image save */
  return 0;
}