inline int round(double n)
{
   return int((n >= 0.0) ? n + 0.5 : n - 0.5);
}

#define pi 3.1415926536

/* rotates points 45deg to make a diamond from a square */
inline void rotate(int half, int x, int y, int &rx, int &ry)
{
   double r, theta;

   /* Make center origin */
   x -= half;
   y = half - y;

   r = sqrt(x * x + y * y);
   theta = atan2(y, x);   //sweet!
   theta += pi / 4;

   /* Convert back to upper-left origin */
   rx = round(r * cos(theta)) + half;
   ry = round(r * sin(theta)) + half;
}

void rotate(int px, int py, int xi, int yi, int &xo, int &yo, int angle)
{
    /* convert to radians */
    double ang = round((double)angle * 3.1415926535898 / 180.0);

    xo = px + round((double)(xi - px) * cos(ang) - (double)(yi - py) * sin(ang));
    yo = py + round((double)(xi - px) * sin(ang) - (double)(yi - py) * cos(ang));
}