def serialize_ndarray_b64(o):
    """
    Serializes a :obj:`numpy.ndarray` in a format where the datatype and shape are
    human-readable, but the array data itself is binary64 encoded.

    Args:
        o (:obj:`numpy.ndarray`): :obj:`ndarray` to be serialized.

    Returns:
        A dictionary that can be passed to :obj:`json.dumps`.
    """
    if o.flags['C_CONTIGUOUS']:
        o_data = o.data
    else:
        o_data = np.ascontiguousarray(o).data
    data_b64 = base64.b64encode(o_data)
    return dict(
        _type='np.ndarray',
        data=data_b64.decode('utf-8'),
        dtype=o.dtype,
        shape=o.shape)