/* lin_hst.c */
#include <stdio.h>
#include <stdlib.h>
#include "mypgm.h"

void linear_transform_histogram( )
     /* linear transformation as applied to graylevel histogram */
     /* input image1[y][x] ===> output image2[y][x] */
{
  int min, max; /* maximum & minimum graylevels */
  int x, y;     /* Loop variables */
  
  /* detection of maximum & minimum values of gray levels */
  min = max = image1[0][0];
  for (y = 0; y < y_size1; y++) {
    for (x = 0; x < x_size1; x++) {
      if (image1[y][x] < min) min = image1[y][x];
      if (image1[y][x] > max) max = image1[y][x];
    }
  }
  printf("Minimum graylevel = %d --- Maximum graylevel = %d\n", min, max);
  if ((max - min) == 0) {
    printf("Nothing in image!!!\n\n");
    exit(1);
  }
  
  /* result of linear transformation stored into image2[y][x] */
  x_size2 = x_size1;
  y_size2 = y_size1;
  for (y = 0; y < y_size1; y++) {
    for (x = 0; x < x_size1; x++) {
      image2[y][x] = (unsigned char)((image1[y][x] - min)
				     * MAX_BRIGHTNESS / (max - min));
    }
  }
}

main( )
{
  load_image_data( );            /* input image1 */
  linear_transform_histogram( ); /* linear transformation of histogram */
  save_image_data( );            /* output image2 */
  return 0;
}