中文说明：最基本的由彩色图像转换为灰度图像的代码。在matlab中运行图像处理时用到的最基本源码，但是很多matlab中并不含有这个函数。
English Description：
The most basic by the color image into gray image code. Running image processing in MATLAB is the most basic source code, but many matlab does not contain this function.