图像灰度值的计算 http://blog.youkuaiyun.com/godenlove007/article/details/7604164 图像的灰度化原理和实现 http://blog.youkuaiyun.com/chenamo9651/article/details/88669 VC++ 灰度位图处理 http://www.cxy.me/doc/3167.htm