Calculates an envelopping rectangle for a xyiArray.
an envelopping rectangle
xyiArray A = new xyiArray(4); A[0] = new xyi(-4, 2); A[1] = new xyi(24, 12); A[2] = new xyi(4, -3); A[3] = new xyi(5, 11); Rectangle r = Maxrect(Rectangle.Reset()); // now //r.Left = -4; //r.Top = -3; //r.Right = 24; //r.Down = 12;