http://hunan.wudingfadian.com/
http://www.cnblogs.com/Darksun/p/5170014.html
http://www.cnblogs.com/cs-player1/p/5169307.html
https://github.com/Darksun2010/MLlearning/tree/master/kNN/digits/testDigits
原文：http://www.cnblogs.com/pengkunfan/p/5170270.html