#include "ReadBMP.h"  #include "resource.h"  #include <afxdlgs.h >    CMyApp theApp;  BOOL CMyApp::InitInstance()  {      m_pMainWnd = new CMainWindow;      m_pMainWnd->ShowWindow(m_nCmdShow);      return TRUE; //必须返回TRUE,否则不会进入消息循环，界面会直接退出  }    //CMainWindow  BEGIN_MESSAGE_MAP(CMainWindow, CWnd)  ON_WM_CREATE()  ON_WM_PAINT()  ON_COMMAND(IDC_OPEN, OnOpen)  END_MESSAGE_MAP()  //构造函数  CMainWindow::CMainWindow()  {      LPCTSTR lpszClassName = ::AfxRegisterWndClass(CS_HREDRAW|CS_VREDRAW, ::LoadCursorA(NULL, IDC_ARROW), (HBRUSH)(COLOR_3DFACE+1), theApp.LoadIcon(IDI_MAIN));      CreateEx(WS_EX_CLIENTEDGE, lpszClassName, "xxx", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL);  }  //析构函数  CMainWindow::~CMainWindow()  {    }  //消息映射函数  int CMainWindow::OnCreate(LPCREATESTRUCT lpCreateStruct)  {      //OutputDebugString("oncreate");      CClientDC dc(this);      m_hMemDC = ::CreateCompatibleDC(dc);      m_nWidth = 0;      m_nHeight = 0;      //设置菜单      HMENU hMenu = ::LoadMenuA(theApp.m_hInstance, (LPCSTR)IDR_MENU);      ::SetMenu(m_hWnd, hMenu);      return 0;  }    void CMainWindow::OnNcDestroy( )  {      delete this;  }  void CMainWindow::OnDestroy()  {        }  void CMainWindow::OnPaint()  {      CPaintDC dc(this);      ::BitBlt(dc, 0, 0, m_nWidth, m_nHeight, m_hMemDC, 0, 0, SRCCOPY);  }  void CMainWindow::OnOpen()  {      CFileDialog dlg(TRUE);      if (IDOK != dlg.DoModal())      {          return;      }      HANDLE  hFile = ::CreateFile(dlg.GetPathName(), GENERIC_READ , FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);      if (INVALID_HANDLE_VALUE == hFile)      {          return;      }      HANDLE  hFileMap = ::CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);      if (NULL == hFileMap)      {          return;      }      LPVOID lpBase = ::MapViewOfFile(hFileMap, FILE_MAP_READ, 0, 0, 0);      if (NULL == lpBase)      {          return;      }      //从头结构中取三个信息：1.bfOffBits位图数据在文件中的起始位置，2.m_nWidth图像的宽，3.m_nHeight图像的高      BITMAPFILEHEADER* pbitmapFileHeader;      BITMAPINFO* pbitmapInfo;      pbitmapFileHeader = (BITMAPFILEHEADER*)lpBase;      if (pbitmapFileHeader->bfType != MAKEWORD('B','M'))      {          MessageBox("not bmp");          ::UnmapViewOfFile(lpBase);          ::CloseHandle(hFileMap);          ::CloseHandle(hFile);      }      //DWORD bfOffBits = pbitmapFileHeader->bfOffBits;      BYTE* pBits = (BYTE*)lpBase + pbitmapFileHeader->bfOffBits;      pbitmapInfo = (BITMAPINFO*)((BYTE*)lpBase + sizeof(BITMAPFILEHEADER));      m_nWidth = pbitmapInfo->bmiHeader.biWidth;      m_nHeight = pbitmapInfo->bmiHeader.biHeight;      //显示BMP文件到内存设备      //得客户区DC      CClientDC dc(this);      //创建与客户区DC兼容的位图      HBITMAP hBitmap = ::CreateCompatibleBitmap(dc, m_nWidth, m_nHeight);      if (hBitmap == 0)      {          return;      }      //位图选入内存DC      ::SelectObject(m_hMemDC, hBitmap);        //图像数据放到建立的DC中      ::SetDIBitsToDevice(m_hMemDC, 0, 0, m_nWidth, m_nHeight, 0, 0, 0, m_nHeight, pBits, pbitmapInfo, DIB_RGB_COLORS);        ::InvalidateRect(m_hWnd, NULL, TRUE);      ::DeleteObject(hBitmap);        ::UnmapViewOfFile(lpBase);      ::CloseHandle(hFileMap);      ::CloseHandle(hFile);    }

#include <afxwin.h>    class CMyApp:public CWinApp  {  public:      virtual BOOL InitInstance();  };    //CMainWindow  class CMainWindow:public CWnd  {  public:      CMainWindow();      ~CMainWindow();    protected:      HDC m_hMemDC; //与客户区兼容的内存DC句柄       UINT m_nWidth; //BMP的宽度      UINT m_nHeight; //BMP的高度            //消息映射      afx_msg void OnNcDestroy( );      afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);      afx_msg void OnDestroy( );      afx_msg void OnOpen();      afx_msg void OnPaint();      DECLARE_MESSAGE_MAP()  };