def _sim_fill(r1, r2, imsize):
    """
        calculate the fill similarity over the image
    """
    bbsize = (max(r1['max_x'], r2['max_x']) - min(r1['min_x'], r2['min_x'])
        ) * (max(r1['max_y'], r2['max_y']) - min(r1['min_y'], r2['min_y']))
    return 1.0 - (bbsize - r1['size'] - r2['size']) / imsize
