def boundary_polygon(self, time):
        """
        Get coordinates of object boundary in counter-clockwise order
        """
        ti = np.where(time == self.times)[0][0]
        com_x, com_y = self.center_of_mass(time)
        # If at least one point along perimeter of the mask rectangle is unmasked, find_boundaries() works.
        # But if all perimeter points are masked, find_boundaries() does not find the object.
        # Therefore, pad the mask with zeroes first and run find_boundaries on the padded array.
        padded_mask = np.pad(self.masks[ti], 1, 'constant', constant_values=0)
        chull = convex_hull_image(padded_mask)
        boundary_image = find_boundaries(chull, mode='inner', background=0)
        # Now remove the padding.
        boundary_image = boundary_image[1:-1,1:-1]
        boundary_x = self.x[ti].ravel()[boundary_image.ravel()]
        boundary_y = self.y[ti].ravel()[boundary_image.ravel()]
        r = np.sqrt((boundary_x - com_x) ** 2 + (boundary_y - com_y) ** 2)
        theta = np.arctan2((boundary_y - com_y), (boundary_x - com_x)) * 180.0 / np.pi + 360
        polar_coords = np.array([(r[x], theta[x]) for x in range(r.size)], dtype=[('r', 'f4'), ('theta', 'f4')])
        coord_order = np.argsort(polar_coords, order=['theta', 'r'])
        ordered_coords = np.vstack([boundary_x[coord_order], boundary_y[coord_order]])
        return ordered_coords
Get coordinates of object boundary in counter-clockwise order