#define ABS(x)         ((x) > 0 ? (x) : (-x))
void linedraw(int x0, int y0, int x1, int y1, int *xout, int *yout)
{
  int x = x0, y = y0;
  int dx = ABS(x1-x0), sx = x0<x1 ? 1 : -1;
  int dy = ABS(y1-y0), sy = y0<y1 ? 1 : -1;
  int err = ((dx>dy) ? dx : -dy)/2, e2;
  for (;;)
  {
    *xout = x;
    *yout = y;
//    SETPIXEL(x, y);
    if (x==x1 && y==y1) 
    {
      break;
    }
    e2 = err;
    if (e2 >-dx) 
    { 
      err -= dy; 
      x += sx; 
    }
    if (e2 < dy) 
    { 
      err += dx; 
      y += sy; 
    }
  }
}