/*********************************************************/
/*   program 15: laplacian edge enhancement              */
/*********************************************************/

#define  XSIZE  640
#define  YSIZE  480

#define  LSIGN  1    /* treat result as signed pixels */
#define  LPOS   2    /* ignore negative values */
#define  LGREY  3    /* offset negative values */

main()
  {
  unsigned char *in;
  unsigned char *out;
  unsigned char *i1,*i2,*i3;
  unsigned char *o;
  long  int  x,y;
  long  int  val,method;

  /* indicate how to interpret results */
  method = LSIGN;

  /* allocate input and output memory buffers */
  in  = (unsigned char *) malloc (XSIZE*YSIZE);
  out = (unsigned char *) malloc (XSIZE*YSIZE);

  /* read the input image (one plane) */
  read_image("input",in);

  /* process all lines in the image */
  for (y = 1; y < (YSIZE-1); y++)
    {
    i1 = in + ((y-1)*XSIZE);
    i2 = i1 + XSIZE;
    i3 = i2 + XSIZE;
    o  = out + (y*XSIZE) + 1;

    /* process all pixels in the line */
    for (x = 1; x < (XSIZE-1); x++)
      {
      val = (((long int)*(i2+1) & 0xff)<< 3) -
             ((long int)*(i1+0) & 0xff) -
             ((long int)*(i1+1) & 0xff) -
             ((long int)*(i1+2) & 0xff) -
             ((long int)*(i2+0) & 0xff) -
             ((long int)*(i2+2) & 0xff) -
             ((long int)*(i3+0) & 0xff) -
             ((long int)*(i3+1) & 0xff) -
             ((long int)*(i3+2) & 0xff);

      /* interpret results of output pixel */
      switch (method)
        {
        case LSIGN:
          val = val / 24;
          break;
        case LPOS:
          if (val > 255) val = 255;
          if (val <   0) val = 0;
          break;
        case LGREY:
          if (val >  127) val =  127;
          if (val < -128) val = -128;
          val = val + 128;
          break;
        default:
          break;
        }

      /* save processed output pixel */
      *o++ = (unsigned int)val;
      i1++;
      i2++;
      i3++;
      }
    }

  /* write the output image (one plane) */
  write_image("output",out);

/* 
  Free memory buffers.
*/
  free(in);
  free(out);

}