code: def _quadPoints(size, disp1, disp2):
          
          w, h = size
          x1, y1 = disp1
          x2, y2 = disp2
  
          return (
              x1,    -y1,
              -x1,    h + y2,
              w + x2, h - y2,
              w - x2, y1
          )
docs: Return points for QUAD transformation.