OpenCV——计算轮廓长度/周长和面积

参考：
https://blog.csdn.net/B08370108/article/details/118106598?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163532692116780274193196%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=163532692116780274193196&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allfirst_rank_ecpm_v1~rank_v31_ecpm-7-118106598.first_rank_v2_pc_rank_v29&utm_term=opencv+计算轮廓面积&spm=1018.2226.3001.4187

https://blog.csdn.net/weixin_41713230/article/details/83013524?ops_request_misc=&request_id=&biz_id=102&utm_term=opencv图像分割，面积&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduweb~default-0-83013524.first_rank_v2_pc_rank_v29&spm=1018.2226.3001.4187