def get_roi_center(roi_reference, roi_size):
    """
    Returns the coordiantes of ROI center.

    :param roi_reference: (y, x) coordinates of ROI upper-left vertex.
    :param roi_size: (y. x) size of ROI.
    :return roi_center: (y, x) coordinates of ROI center pixel.
    """
    return roi_reference[0] + roi_size[0] // 2, roi_reference[1] + roi_size[1
        ] // 2
