说明：  做安卓图像处理相关开发的时候，实现的在图片上画线的功能，类似matlab上的plot（）函数，还有hold on。 做安卓图像处理的同学一定会喜欢的。
(When do Android image processing development, draw lines on the picture to achieve functionality similar to matlab plot() function, as well as hold on. someone do Android image processing will like this.)