/*********************************************************/
/*   program 2: convert rgb to cym                       */
/*********************************************************/


#define  MAX    255
#define  XSIZE  640
#define  YSIZE  480

unsigned char *ir,*ig,*ib;
unsigned char *oc,*om,*oy;

main()
  {
  long  int  x,y;

  /* allocate input and output memory buffers */
  ir = (unsigned char *) malloc (XSIZE*YSIZE);
  ig = (unsigned char *) malloc (XSIZE*YSIZE);
  ib = (unsigned char *) malloc (XSIZE*YSIZE);
  oc = (unsigned char *) malloc (XSIZE*YSIZE);
  om = (unsigned char *) malloc (XSIZE*YSIZE);
  oy = (unsigned char *) malloc (XSIZE*YSIZE);

  /* read the rgb input image */
  read_image("input",ir,ig,ib);

  /* convert each pixel to cym */
  for (y = 0; y < YSIZE; y = y++)
    {
    for (x = 0; x < XSIZE; x = x++)
      {
      oc[(y*XSIZE)+x] = MAX - ir[(y*XSIZE)+x];  /* cyan */
      om[(y*XSIZE)+x] = MAX - ig[(y*XSIZE)+x];  /* magenta */
      oy[(y*XSIZE)+x] = MAX - ib[(y*XSIZE)+x];  /* yellow */
      }
    }

  /* write the output image */
  /* note: if the output image is displayed on an rgb monitor
      it will appear like a negative, but if it is printed on
      a cym printer it will appear correct. */
  write_image("output",oc,oy,om);

  /* free memory buffers */
  free (ir);
  free (ig);
  free (ib);
  free (oc);
  free (om);
  free (oy);
}