/*********************************************************/
/*   program 17: unsharp masking filter                  */
/*********************************************************/

#define  XSIZE  640
#define  YSIZE  480

#define  RED    0
#define  GREEN  1
#define  BLUE   2

#define  LPASS  3    /* 3, 5, 7, 9, ... */
#define  WEIGHT 0.7  /* between 0.6 and 0.9 */

main()
  {
  unsigned char *ir,*ig,*ib;
  unsigned char *lr,*lg,*lb;
  unsigned char *or,*og,*ob;
  unsigned char *i,*i1,*i2,*i3;
  unsigned char *l,*l1;
  unsigned char *o;
  long  int  x,y,c;
  long  int  xm,ym;
  long  int  val;
  float      cp,cl,fval;

  /* allocate input and output memory buffers */
  ir = (unsigned char *) malloc (XSIZE*YSIZE);
  ig = (unsigned char *) malloc (XSIZE*YSIZE);
  ib = (unsigned char *) malloc (XSIZE*YSIZE);
  lr = (unsigned char *) malloc (XSIZE*YSIZE);
  lg = (unsigned char *) malloc (XSIZE*YSIZE);
  lb = (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);

  /* create low-pass filtered image */
  for (c = RED; c <= BLUE; c++)
    {
    if (c == RED  ) i = ir;
    if (c == GREEN) i = ig;
    if (c == BLUE ) i = ib;
    if (c == RED  ) l = lr;
    if (c == GREEN) l = lg;
    if (c == BLUE ) l = lb;
    for (y = (LPASS/2); y < (YSIZE-(LPASS/2)); y++)
      {
      i1 = i + (y*XSIZE) + (LPASS/2);
      l1 = l + (y*XSIZE) + (LPASS/2);
      for (x = (LPASS/2); x < (XSIZE-(LPASS/2)); x++)
        {
        i2 = i1 - ((LPASS/2)*XSIZE) - (LPASS/2);
        val = 0;
        for (ym = 0; ym < LPASS; ym++)
          {
          i3 = i2 + (ym*XSIZE);
          for (xm = 0; xm < LPASS; xm++)
            {
            val = val + ((long int)*i3++ & 0xff);
            }
          }
        *l1++ = (unsigned char)(val / (LPASS*LPASS));
        i1++;
        }
      }
    }

  /* calculate constants for image merge */
  cp = WEIGHT / ((2.0 * WEIGHT) - 1.0);
  cl = (1.0 - WEIGHT) / ((2.0 * WEIGHT) - 1.0);

  /* process the red, green, and blue planes one at a time */
  for (c = RED; c <= BLUE; c++)
    {
    /* initialize pointers for current color plane */
    if (c == RED  ) i = ir;
    if (c == GREEN) i = ig;
    if (c == BLUE ) i = ib;
    if (c == RED  ) l = lr;
    if (c == GREEN) l = lg;
    if (c == BLUE ) l = lb;
    if (c == RED  ) o = or;
    if (c == GREEN) o = og;
    if (c == BLUE ) o = ob;

    /* merge the original and low-pass images */
    for (y = 0; y < YSIZE; y++)
      {
      for (x = 0; x < XSIZE; x++)
        {
        fval = (cp * (float)*i++) - (cl * (float)*l++);
        if (fval < 0.0)   fval = 0.0;
        if (fval > 255.0) fval = 255.0;
        *o++ = (unsigned char)fval;
        }
      }
    }

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

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