BYTE* pBits = (BYTE*)lpBase + pbitmapFileHeader->bfOffBits;

BYTE* pBits =  pbitmapFileHeader->bfOffBits;

#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; //必須返回TRUE,否則不會進入消息循環，界面會直接退出 
} 
 
//CMainWindow 
BEGIN_MESSAGE_MAP(CMainWindow, CWnd) 
ON_WM_CREATE() 
ON_WM_PAINT() 
ON_COMMAND(IDC_OPEN, OnOpen) 
END_MESSAGE_MAP() 
//構造函數 
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); 
} 
//析構函數 
CMainWindow::~CMainWindow() 
{ 
 
} 
//消息映射函數 
int CMainWindow::OnCreate(LPCREATESTRUCT lpCreateStruct) 
{ 
    //OutputDebugString("oncreate"); 
    CClientDC dc(this); 
    m_hMemDC = ::CreateCompatibleDC(dc); 
    m_nWidth = 0; 
    m_nHeight = 0; 
    //設置菜單 
    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; 
    } 
    //從頭結構中取三個信息：1.bfOffBits位圖數據在文件中的起始位置，2.m_nWidth圖像的寬，3.m_nHeight圖像的高 
    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; 
    //顯示BMP文件到內存設備 
    //得客戶區DC 
    CClientDC dc(this); 
    //創建與客戶區DC兼容的位圖 
    HBITMAP hBitmap = ::CreateCompatibleBitmap(dc, m_nWidth, m_nHeight); 
    if (hBitmap == 0) 
    { 
        return; 
    } 
    //位圖選入內存DC 
    ::SelectObject(m_hMemDC, hBitmap); 
 
    //圖像數據放到建立的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; //與客戶區兼容的內存DC句柄  
    UINT m_nWidth; //BMP的寬度 
    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() 
};