/* FFT2fltr_Low.c */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "mypgm.h"
#include "FFT1.h"
#include "FFT2.h"

void lowpass_filtering( )
{
  int i, j;
  int M;
  double max, radius;
  
  printf("\nLowpass filtering is applied to FFT coefficients.\n");
  printf("Total frequency range is 0 - %d.\n", num_of_data/2);
  while (1) {
    printf("Enter maximum frequency : ");
    scanf("%d", &M);
    if (0 < M && M <= num_of_data/2) break;
    printf("\nOutside the range!\n");
  }
  
  max = pow(M, 2);
  
  for (j = 0; j < num_of_data; j++) {
    for (i = 0; i < num_of_data; i++) {
      radius = pow(i - num_of_data/2, 2) + pow(j - num_of_data/2, 2);
      if (radius > max) {
	data[j][i] = 0.0;
	jdata[j][i] = 0.0;
      }
    }
  }
}


main( )
{
  load_image_data( );      /* Input image load      */
  make_original_data( );   /* FFT arrays generation   */
  FFT2(1);                 /* 2-d FFT  */
  origin_centered_FFT();   /* FFT rearrangement */
  lowpass_filtering( );    /* Lowpass filtering */
  origin_centered_FFT();   /* FFT rearrangement */
  FFT2(-1);                /* 2-d inverse FFT */
  make_output_image_enhanced( );  /* Enhanced image generation after IFFT */
  save_image_data( );      /* Output image save */
  return 0;
}