int internal_reduce()

in matlab/strred/matlabPyrTools/MEX/convolve.c [51:173]
110 lines of code
18 McCabe index (conditional complexity)

int internal_reduce(image, x_dim, y_dim, filt, temp, x_fdim, y_fdim,
		x_start, x_step, x_stop, y_start, y_step, y_stop,
		result, edges)
  register image_type *image, *temp;
  register int x_fdim, x_dim;
  register image_type *result;
  register int x_step, y_step;
  int x_start, y_start;
  int x_stop, y_stop;     
  image_type *filt; 
  int y_dim, y_fdim;
  char *edges;
  { 
  register double sum;
  register int filt_pos, im_pos, x_filt_stop;
  register int x_pos, filt_size = x_fdim*y_fdim;
  register int y_pos, res_pos;
  register int y_ctr_stop = y_dim - ((y_fdim==1)?0:y_fdim);
  register int x_ctr_stop = x_dim - ((x_fdim==1)?0:x_fdim);
  register int x_res_dim = (x_stop-x_start+x_step-1)/x_step;
  int x_ctr_start = ((x_fdim==1)?0:1);
  int y_ctr_start = ((y_fdim==1)?0:1);
  int x_fmid = x_fdim/2;
  int y_fmid = y_fdim/2;
  int base_res_pos;
  fptr reflect = edge_function(edges);  /* look up edge-handling function */

  if (!reflect) return(-1);

  /* shift start/stop coords to filter upper left hand corner */
  x_start -= x_fmid;   y_start -=  y_fmid;
  x_stop -=  x_fmid;   y_stop -=  y_fmid;

  if (x_stop < x_ctr_stop) x_ctr_stop = x_stop;
  if (y_stop < y_ctr_stop) y_ctr_stop = y_stop;

  for (res_pos=0, y_pos=y_start;	      /* TOP ROWS */
       y_pos<y_ctr_start;
       y_pos+=y_step)
    {
    for (x_pos=x_start;			      /* TOP-LEFT CORNER */
	 x_pos<x_ctr_start;
	 x_pos+=x_step, res_pos++)
      {
      (*reflect)(filt,x_fdim,y_fdim,x_pos-1,y_pos-1,temp,REDUCE);
      INPROD(0,0)
      }

    (*reflect)(filt,x_fdim,y_fdim,0,y_pos-1,temp,REDUCE);
    for (;				      /* TOP EDGE */
	 x_pos<x_ctr_stop;
	 x_pos+=x_step, res_pos++) 
      INPROD(x_pos,0)

    for (;				      /* TOP-RIGHT CORNER */
	 x_pos<x_stop;
	 x_pos+=x_step, res_pos++) 
      {
      (*reflect)(filt,x_fdim,y_fdim,x_pos-x_ctr_stop+1,y_pos-1,temp,REDUCE);
      INPROD(x_ctr_stop,0)
      }
    } /* end TOP ROWS */   

  y_ctr_start = y_pos;			      /* hold location of top */
  for (base_res_pos=res_pos, x_pos=x_start;   /* LEFT EDGE */
       x_pos<x_ctr_start;
       x_pos+=x_step, base_res_pos++)
    {
    (*reflect)(filt,x_fdim,y_fdim,x_pos-1,0,temp,REDUCE);
    for (y_pos=y_ctr_start, res_pos=base_res_pos;
	 y_pos<y_ctr_stop;
	 y_pos+=y_step, res_pos+=x_res_dim)
      INPROD(0,y_pos)
    }

  (*reflect)(filt,x_fdim,y_fdim,0,0,temp,REDUCE);
  for (;				      /* CENTER */
       x_pos<x_ctr_stop;
       x_pos+=x_step, base_res_pos++) 
    for (y_pos=y_ctr_start, res_pos=base_res_pos;
	 y_pos<y_ctr_stop;
	 y_pos+=y_step, res_pos+=x_res_dim)
      INPROD(x_pos,y_pos)

  for (;				      /* RIGHT EDGE */
       x_pos<x_stop;
       x_pos+=x_step, base_res_pos++)
    {
    (*reflect)(filt,x_fdim,y_fdim,x_pos-x_ctr_stop+1,0,temp,REDUCE);
    for (y_pos=y_ctr_start, res_pos=base_res_pos;
	 y_pos<y_ctr_stop;
	 y_pos+=y_step, res_pos+=x_res_dim)
      INPROD(x_ctr_stop,y_pos)
    }

  for (res_pos-=(x_res_dim-1);
       y_pos<y_stop;			      /* BOTTOM ROWS */
       y_pos+=y_step) 
    {
    for (x_pos=x_start;			      /* BOTTOM-LEFT CORNER */
	 x_pos<x_ctr_start;
	 x_pos+=x_step, res_pos++)
      {
      (*reflect)(filt,x_fdim,y_fdim,x_pos-1,y_pos-y_ctr_stop+1,temp,REDUCE);
      INPROD(0,y_ctr_stop)
      }

    (*reflect)(filt,x_fdim,y_fdim,0,y_pos-y_ctr_stop+1,temp,REDUCE);
    for (;				      /* BOTTOM EDGE */
	 x_pos<x_ctr_stop;
	 x_pos+=x_step, res_pos++) 
      INPROD(x_pos,y_ctr_stop)

    for (;				      /* BOTTOM-RIGHT CORNER */
	 x_pos<x_stop;
	 x_pos+=x_step, res_pos++) 
      {
      (*reflect)(filt,x_fdim,y_fdim,x_pos-x_ctr_stop+1,y_pos-y_ctr_stop+1,temp,REDUCE);
      INPROD(x_ctr_stop,y_ctr_stop)
      }
    } /* end BOTTOM */
  return(0);
  } /* end of internal_reduce */