MFC的CBitmap不支持直接从文件读取BMP，且不支持拷贝构造和赋值，CSystemBitmap继承自CBitmap添加如下功能： LoadBitmapFromFile: 从文件读取BMP GetBitmapSize: 获取BMP大小拷贝构造与赋值= -MFC-CBitmap does not support directly from the file to read BMP, and does not support the c