def flowread(flow_or_path, quantize=False, concat_axis=0, *args, **kwargs):
    """Read an optical flow map.

    Args:
        flow_or_path (ndarray or str): A flow map or filepath.
        quantize (bool): whether to read quantized pair, if set to True,
            remaining args will be passed to :func:`dequantize_flow`.
        concat_axis (int): The axis that dx and dy are concatenated,
            can be either 0 or 1. Ignored if quantize is False.

    Returns:
        ndarray: Optical flow represented as a (h, w, 2) numpy array
    """
    if isinstance(flow_or_path, np.ndarray):
        if (flow_or_path.ndim != 3) or (flow_or_path.shape[-1] != 2):
            raise ValueError('Invalid flow with shape {}'.format(
                flow_or_path.shape))
        return flow_or_path
    elif not is_str(flow_or_path):
        raise TypeError(
            '"flow_or_path" must be a filename or numpy array, not {}'.format(
                type(flow_or_path)))

    if not quantize:
        with open(flow_or_path, 'rb') as f:
            try:
                header = f.read(4).decode('utf-8')
            except Exception:
                raise IOError('Invalid flow file: {}'.format(flow_or_path))
            else:
                if header != 'PIEH':
                    raise IOError(
                        'Invalid flow file: {}, header does not contain PIEH'.
                        format(flow_or_path))

            w = np.fromfile(f, np.int32, 1).squeeze()
            h = np.fromfile(f, np.int32, 1).squeeze()
            flow = np.fromfile(f, np.float32, w * h * 2).reshape((h, w, 2))
    else:
        assert concat_axis in [0, 1]
        cat_flow = imread(flow_or_path, flag='unchanged')
        if cat_flow.ndim != 2:
            raise IOError(
                '{} is not a valid quantized flow file, its dimension is {}.'.
                format(flow_or_path, cat_flow.ndim))
        assert cat_flow.shape[concat_axis] % 2 == 0
        dx, dy = np.split(cat_flow, 2, axis=concat_axis)
        flow = dequantize_flow(dx, dy, *args, **kwargs)

    return flow.astype(np.float32)
Read an optical flow map.

    Args:
        flow_or_path (ndarray or str): A flow map or filepath.
        quantize (bool): whether to read quantized pair, if set to True,
            remaining args will be passed to :func:`dequantize_flow`.
        concat_axis (int): The axis that dx and dy are concatenated,
            can be either 0 or 1. Ignored if quantize is False.

    Returns:
        ndarray: Optical flow represented as a (h, w, 2) numpy array