/*********************************************************/
/*   program 1: modify depth resolution                  */
/*********************************************************/

#include "math.h"
#define  DEPTH  3
#define  XSIZE  640
#define  YSIZE  480

unsigned char *ir,*ig,*ib;
unsigned char *or,*og,*ob;

main()
  {
  long int x, y;
  float scale;

  /* allocate input and output memory buffers */
  ir = (unsigned char *) malloc (XSIZE*YSIZE);
  ig = (unsigned char *) malloc (XSIZE*YSIZE);
  ib = (unsigned char *) malloc (XSIZE*YSIZE);
  or = (unsigned char *) malloc (XSIZE*YSIZE);
  og = (unsigned char *) malloc (XSIZE*YSIZE);
  ob = (unsigned char *) malloc (XSIZE*YSIZE);

  /* read the input image (8-bit resolution) */
  read_image("input",ir,ig,ib);

  /* calculate the scale factor that will reduce 8-bit values
      (0-255, inclusive) to evenly spaced values of 0-255 for
      the requested depth resolution. */
  /* example: if DEPTH = 2, values are 0, 85, 171, and 255 */
  scale = 255.0 / (powf (2.0, (float)DEPTH) - 1.0);

  /* reduce depth resolution by generating new 8-bit pixel values */
  for (y = 0; y < YSIZE; y = y++)
    {
    for (x = 0; x < XSIZE; x = x++)
      {
      or[(y*XSIZE)+x] = (ir[(y*XSIZE)+x] >> (8 - DEPTH)) * scale;
      og[(y*XSIZE)+x] = (ig[(y*XSIZE)+x] >> (8 - DEPTH)) * scale;
      ob[(y*XSIZE)+x] = (ib[(y*XSIZE)+x] >> (8 - DEPTH)) * scale;
      }
    }

  /* write the output image */
  write_image("output",or,og,ob);

  /* free memory buffers */
  free (ir);
  free (ig);
  free (ib);
  free (or);
  free (og);
  free (ob);
}