以下代码13行为什么报错：NoneType object has no attribute ndimimport cv2 as cvimport numpy as npimport matplotlibpyplot as pltdef showimg if imgndim == 2 pltimshowimg cmap=gray else pltimshowc

可能是因为没有找到任何轮廓，导致变量cnts和hiers都被赋值为None，所以在执行cv.drawContours(mask,cnts,0,255,-1)时出现了'NoneType' object has no attribute 'ndim'的错误。需要在执行findContours之前增加判断，确保找到了轮廓再进行操作。