def flow2rgb(flow, color_wheel=None, unknown_thr=1e6):
    """Convert flow map to RGB image.

    Args:
        flow (ndarray): Array of optical flow.
        color_wheel (ndarray or None): Color wheel used to map flow field to
            RGB colorspace. Default color wheel will be used if not specified.
        unknown_thr (str): Values above this threshold will be marked as
            unknown and thus ignored.

    Returns:
        ndarray: RGB image that can be visualized.
    """
    assert flow.ndim == 3 and flow.shape[-1] == 2
    if color_wheel is None:
        color_wheel = make_color_wheel()
    assert color_wheel.ndim == 2 and color_wheel.shape[1] == 3
    num_bins = color_wheel.shape[0]

    dx = flow[:, :, 0].copy()
    dy = flow[:, :, 1].copy()

    ignore_inds = (
        np.isnan(dx) | np.isnan(dy) | (np.abs(dx) > unknown_thr) |
        (np.abs(dy) > unknown_thr))
    dx[ignore_inds] = 0
    dy[ignore_inds] = 0

    rad = np.sqrt(dx**2 + dy**2)
    if np.any(rad > np.finfo(float).eps):
        max_rad = np.max(rad)
        dx /= max_rad
        dy /= max_rad

    rad = np.sqrt(dx**2 + dy**2)
    angle = np.arctan2(-dy, -dx) / np.pi

    bin_real = (angle + 1) / 2 * (num_bins - 1)
    bin_left = np.floor(bin_real).astype(int)
    bin_right = (bin_left + 1) % num_bins
    w = (bin_real - bin_left.astype(np.float32))[..., None]
    flow_img = (1 -
                w) * color_wheel[bin_left, :] + w * color_wheel[bin_right, :]
    small_ind = rad <= 1
    flow_img[small_ind] = 1 - rad[small_ind, None] * (1 - flow_img[small_ind])
    flow_img[np.logical_not(small_ind)] *= 0.75

    flow_img[ignore_inds, :] = 0

    return flow_img
Convert flow map to RGB image.

    Args:
        flow (ndarray): Array of optical flow.
        color_wheel (ndarray or None): Color wheel used to map flow field to
            RGB colorspace. Default color wheel will be used if not specified.
        unknown_thr (str): Values above this threshold will be marked as
            unknown and thus ignored.

    Returns:
        ndarray: RGB image that can be visualized.
    
ControlNet-v1-1-nightly/annotator/uniformer/mmcv/visualization/optflow.py