def Nxxyy2yolo(xmin, xmax, ymin, ymax):
    """convert normalised xxyy OID format to yolo format"""

    ratio_cx = (xmin + xmax)/2
    ratio_cy = (ymin + ymax)/2
    ratio_bw = xmax - xmin
    ratio_bh = ymax - ymin

    return (ratio_cx, ratio_cy, ratio_bw, ratio_bh)