mean shift :
https://www.jianshu.com/p/f9d8e566ab18
https://www.cnblogs.com/developerdaily/p/9284093.html
http://www.360doc.com/content/19/0623/22/99071_844418459.shtml
https://www.jianshu.com/p/332828aece2f
https://blog.csdn.net/google19890102/article/details/51030884
https://www.cnblogs.com/feffery/p/8596482.html
https://www.jianshu.com/p/f9d8e566ab18
http://www.360doc.com/content/19/0623/22/99071_844418459.shtml
agglomerative clustering
https://blog.csdn.net/ycy0706/article/details/90439245
https://blog.csdn.net/leonliu1995/article/details/78944798