/*********************************************************/
/*   program 10: apply look-up table                     */
/*********************************************************/

#define  XSIZE  640
#define  YSIZE  480

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

main()
  {
  long  int  x,y,i;
  unsigned char lut[256];

  /* 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 */
  read_image("input",ir,ig,ib);

  /* initialize look-up table (invert, for this example) */
  for (i = 0; i <= 255; i++) lut[i] = 255 - i;

  /* apply look-up table to each pixel in image */
  for (y = 0; y < YSIZE; y++)
    {
    for (x = 0; x < XSIZE; x++)
      {
      or[(y*XSIZE)+x] = lut[ir[(y*XSIZE)+x]];
      og[(y*XSIZE)+x] = lut[ig[(y*XSIZE)+x]];
      ob[(y*XSIZE)+x] = lut[ib[(y*XSIZE)+x]];
      }
    }

  /* 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);
}