def transform(self, X=None, y=None):
        """
        Transform an image using an Affine transform with the given
        rotation parameters.   Return the transform if X=None.

        Arguments
        ---------
        X : ANTsImage
            Image to transform

        y : ANTsImage (optional)
            Another image to transform

        Returns
        -------
        ANTsImage if y is None, else a tuple of ANTsImage types

        Examples
        --------
        >>> import ants
        >>> img = ants.image_read(ants.get_data('r16'))
        >>> tx = ants.contrib.Rotate2D(rotation=(10,-5,12))
        >>> img2 = tx.transform(img)
        """
        # unpack zoom range
        rotation = self.rotation

        # Rotation about X axis
        theta = math.pi / 180 * rotation
        rotation_matrix = np.array([[np.cos(theta), -np.sin(theta), 0],
                                    [np.sin(theta),  np.cos(theta), 0]])

        self.tx.set_parameters(rotation_matrix)
        if self.lazy or X is None:
            return self.tx
        else:
            return self.tx.apply_to_image(X, reference=self.reference)