def to_visfmt(annot):
    """
    Helper function that changes (tw,th,bw,bh) -> (tw,th,w,h).
    Used to convert annotations from ilsvr to visdrone's since most scripts are already
    written in visdrone's format.
    """
    
    #Check if it's an empty bbox (neg scene)
    if len(annot) > 1:
        load = [annot[0], annot[1], annot[2]-annot[0], annot[3]-annot[1]]
    else:
        load = [0,0,0,0]
        
    return load