error C2664: 'cvSetMouseCallback' : cannot convert parameter 2 from 'void (int,int,int,int,void *)'

今天想用OpenCV的cvSetMouseCallback'函数来写截图程序，但是编译时老是出现题目那种错误。在网上浏览了好多网页，终于找到相关的论文，基本都说把回调函数写成全局变量。即把 void cvMouseCallback(int mouseEvent,int x,int y,int flags,void* param)改成static void cvMouseCallback(int mouseEvent,int x,int y,int flags,void* param)。

我改了以后出现了很多错误：

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(257) : error C2597: illegal reference to data member 'CMyDlg::pt1' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(258) : error C2597: illegal reference to data member 'CMyDlg::pt2' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(259) : error C2597: illegal reference to data member 'CMyDlg::is_selecting' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(262) : warning C4551: function call missing argument list

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(262) : error C2597: illegal reference to data member 'CMyDlg::is_selecting' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(263) : error C2597: illegal reference to data member 'CMyDlg::pt2' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(266) : error C2597: illegal reference to data member 'CMyDlg::pt2' in a static member function

C:\Users\Administrator\Desktop\模式识别1\模式识别Dlg.cpp(267) : error C2597: illegal reference to data member 'CMyDlg::is_selecting' in a static member function

原来把cvMouseCallback改成全局函数以后，我所调用的变量也要是静态的，于是我在所有变量前面加上static如：

static CvPoint pt1;

static CvPoint pt2;

static bool is_selecting;

但是又出现问题了

模式识别Dlg.obj : error LNK2001: unresolved external symbol "public: static bool CMyDlg::is_selecting" (?is_selecting@CMyDlg@@2_NA)

模式识别Dlg.obj : error LNK2001: unresolved external symbol "public: static struct CvPoint CMyDlg::pt2" (?pt2@CMyDlg@@2UCvPoint@@A)

模式识别Dlg.obj : error LNK2001: unresolved external symbol "public: static struct CvPoint CMyDlg::pt1" (?pt1@CMyDlg@@2UCvPoint@@A)

原来是变量是静态变量，但是返回值不是static型的，所以我干脆把它移到类之外，作为全局变量，最后编译成功。