/* histogram.c */
#include <stdio.h>
#include <stdlib.h>
#include "mypgm.h"
#define IMAGESIZE 256   /* = GRAYLEVEL */

void make_histogram_image( )
/* Histogram of image1 is output into image2 */
{
  long int histogram[GRAYLEVEL];
  long int max_frequency; /* Maximum frequency */
  int i, j, x, y; /* control variable */
  int height; /* height of histogram */
  int top; /* the most frequent graylevel */
  
  /* Calculation of histogram */
  for (i = 0; i < GRAYLEVEL; i++) {
    histogram[i] = 0;
  }
  printf("Now, histogram of input image is calculated\n\n");
  for (y = 0; y < y_size1; y++) {
    for (x = 0; x < x_size1; x++) {
      histogram[image1[y][x]]++;
    }
  }
  /* calculation of maximum frequency */
  max_frequency = histogram[0];
  top = 0;
  for (i = 1; i < GRAYLEVEL; i++) {
    if (histogram[i] > max_frequency) { 
      max_frequency = histogram[i];
      top = i;
    }
  }
  printf("Maximum frequency = %d at level of %d\n\n", max_frequency, top);
  /* Histogram image generation */
  x_size2 = IMAGESIZE;
  y_size2 = IMAGESIZE;
  for (y = 0; y < y_size2; y++) {
    for (x = 0; x < x_size2; x++) {
      image2[y][x] = 0;
    }
  }
  for (i = 0; i < GRAYLEVEL; i++) {
    height = (int)(MAX_BRIGHTNESS / 
		   (double)max_frequency * (double)histogram[i]);
    for (j = 0; j < height; j++) {
      image2[IMAGESIZE-1-j][i] = MAX_BRIGHTNESS;
    }
  }
}


main( )
{
  load_image_data( );      /* Input of image1 */
  make_histogram_image( ); /* Histogram generation */
  save_image_data( );      /* Output of image2 */
  return 0;
}