Compute lower left `xy` position.

        This is used for the conversion to matplotlib in ``as_artist``

        Taken from http://photutils.readthedocs.io/en/latest/_modules/photutils/aperture/rectangle.html#RectangularAperture.plot

def _lower_left_xy(self):
        """
        Compute lower left `xy` position.

        This is used for the conversion to matplotlib in ``as_artist``

        Taken from http://photutils.readthedocs.io/en/latest/_modules/photutils/aperture/rectangle.html#RectangularAperture.plot
        """
        hw = self.width / 2.
        hh = self.height / 2.
        sint = np.sin(self.angle)
        cost = np.cos(self.angle)
        dx = (hh * sint) - (hw * cost)
        dy = -(hh * cost) - (hw * sint)
        x = self.center.x + dx
        y = self.center.y + dy
        return x, y