Native height of this image, calculated from its height in pixels and
        vertical dots per inch (dpi).

def default_cy(self):
        """
        Native height of this image, calculated from its height in pixels and
        vertical dots per inch (dpi).
        """
        px_height = self.image.px_height
        horz_dpi = self.image.horz_dpi
        height_in_emu = 914400 * px_height / horz_dpi
        return Emu(height_in_emu)