DDA算法
参考:
https://blog.youkuaiyun.com/zhaotianyu950323/article/details/79528172
Bresenham算法
参考:
https://blog.youkuaiyun.com/kakaxi2222/article/details/50708552?utm_source=copy
https://www.cnblogs.com/feiquan/archive/2018/03/04/8506283.html
http://www.cnblogs.com/weiweishuo/archive/2013/03/11/2954443.html