def points_topolar(points, center):
    """Convert points to polar coordinate system.

    Can be either in pixel or real dim, but should be the same for points and center.

    Parameters
    ----------
        points : np.ndarray
            Positions as two column array.
        center : np.ndarray or tuple
            Origin of the polar coordinate system.

    Returns
    -------
        : np.ndarray
            Positions in polar coordinate system as two column array (r, theta).

    """