def generate_ctrlpts2d_weights_file(file_in='', file_out='ctrlpts_weights.txt'):
    """ Generates unweighted control points from weighted ones in 2-D.

    #. Takes in 2-D control points list whose coordinates are organized like (x*w, y*w, z*w, w)
    #. Converts the input control points list into (x, y, z, w) format
    #. Saves the result to a file

    :param file_in: name of the input file (to be read)
    :type file_in: str
    :param file_out: name of the output file (to be saved)
    :type file_out: str
    :raises IOError: an error occurred reading or writing the file
    """
    # Read control points
    ctrlpts2d, size_u, size_v = _read_ctrltps2d_file(file_in)

    # Divide control points by weight
    new_ctrlpts2d = generate_ctrlpts2d_weights(ctrlpts2d)

    # Save new control points
    _save_ctrlpts2d_file(new_ctrlpts2d, size_u, size_v, file_out)