BMP截屏

void CSaveBmpDlg::OnButton1()
{
    // TODO: Add your control notification handler code here
    HWND hWnd = ::GetDesktopWindow();//獲得屏幕的HWND.
    HDC hScreenDC = ::GetDC(hWnd);   //獲得屏幕的HDC.
    int width = ::GetSystemMetrics(SM_CXSCREEN);
    int height = ::GetSystemMetrics(SM_CYSCREEN);
    HBITMAP hBitmap = GetSrcBit(hScreenDC, width, height);
    ASSERT(hBitmap);
    SaveBmp(hBitmap, L"d://screen.bmp");

}
HBITMAP CSaveBmpDlg::GetSrcBit(HDC hDC,DWORD BitWidth, DWORD BitHeight)
{
    HDC hBufDC;
    HBITMAP hBitmap, hBitTemp;
    //創建設備上下文(HDC)
    hBufDC = CreateCompatibleDC(hDC);
    //創建HBITMAP
    hBitmap = CreateCompatibleBitmap(hDC, BitWidth, BitHeight);
    hBitTemp = (HBITMAP) SelectObject(hBufDC, hBitmap);
    //得到位圖緩衝區
    StretchBlt(hBufDC, 0, 0, BitWidth, BitHeight,
        hDC, 0, 0, BitWidth, BitHeight, SRCCOPY);
    //得到最終的位圖信息
    hBitmap = (HBITMAP) SelectObject(hBufDC, hBitTemp);
    //釋放內存
    DeleteObject(hBitTemp);
    ::DeleteDC(hBufDC);
    return hBitmap;
}
BOOL CSaveBmpDlg::SaveBmp(HBITMAP hBitmap, CString FileName)
{
    //設備描述表
    HDC hDC;
    //當前分辨率下每象素所佔字節數
    int iBits;
    //位圖中每象素所佔字節數
    WORD wBitCount;
    //定義調色板大小， 位圖中像素字節大小 ，位圖文件大小 ， 寫入文件字節數
    DWORD dwPaletteSize=0, dwBmBitsSize=0, dwDIBSize=0, dwWritten=0;
    //位圖屬性結構
    BITMAP Bitmap;
    //位圖文件頭結構
    BITMAPFILEHEADER bmfHdr;
    //位圖信息頭結構
    BITMAPINFOHEADER bi;
    //指向位圖信息頭結構
    LPBITMAPINFOHEADER lpbi;
    //定義文件，分配內存句柄，調色板句柄
    HANDLE fh, hDib, hPal,hOldPal=NULL;
    //計算位圖文件每個像素所佔字節數
    hDC = CreateDC("DISPLAY", NULL, NULL, NULL);
    iBits = GetDeviceCaps(hDC, BITSPIXEL) * GetDeviceCaps(hDC, PLANES);
    DeleteDC(hDC);
    if (iBits <= 1) wBitCount = 1;
    else if (iBits <= 4)  wBitCount = 4;
    else if (iBits <= 8)  wBitCount = 8;
    else   wBitCount = 24;
    GetObject(hBitmap, sizeof(Bitmap), (LPSTR)&Bitmap);
    bi.biSize = sizeof(BITMAPINFOHEADER);
    bi.biWidth = Bitmap.bmWidth;
    bi.biHeight = Bitmap.bmHeight;
    bi.biPlanes = 1;
    bi.biBitCount = wBitCount;
    bi.biCompression = BI_RGB;
    bi.biSizeImage = 0;
    bi.biXPelsPerMeter = 0;
    bi.biYPelsPerMeter = 0;
    bi.biClrImportant = 0;
    bi.biClrUsed = 0;
    dwBmBitsSize = ((Bitmap.bmWidth * wBitCount + 31) / 32) * 4 * Bitmap.bmHeight;
    //爲位圖內容分配內存
    hDib = GlobalAlloc(GHND,dwBmBitsSize + dwPaletteSize + sizeof(BITMAPINFOHEADER));
    lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDib);
    *lpbi = bi;

    // 處理調色板
    hPal = GetStockObject(DEFAULT_PALETTE);
    if (hPal)
    {
        hDC = ::GetDC(NULL);
        hOldPal = ::SelectPalette(hDC, (HPALETTE)hPal, FALSE);
        RealizePalette(hDC);
    }
    // 獲取該調色板下新的像素值
    GetDIBits(hDC, hBitmap, 0, (UINT) Bitmap.bmHeight, (LPSTR)lpbi + sizeof(BITMAPINFOHEADER) +dwPaletteSize, (BITMAPINFO *)lpbi, DIB_RGB_COLORS);
    //恢復調色板
    if (hOldPal)
    {
        ::SelectPalette(hDC, (HPALETTE)hOldPal, TRUE);
        RealizePalette(hDC);
        ::ReleaseDC(NULL, hDC);
    }
    //創建位圖文件
    fh = CreateFile(FileName, GENERIC_WRITE,0, NULL, CREATE_ALWAYS,
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);
    if (fh == INVALID_HANDLE_VALUE)  return FALSE;
    // 設置位圖文件頭
    bmfHdr.bfType = 0x4D42; // "BM"
    dwDIBSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + dwPaletteSize + dwBmBitsSize;
    bmfHdr.bfSize = dwDIBSize;
    bmfHdr.bfReserved1 = 0;
    bmfHdr.bfReserved2 = 0;
    bmfHdr.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER) + dwPaletteSize;
    // 寫入位圖文件頭
    WriteFile(fh, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten, NULL);
    // 寫入位圖文件其餘內容
    WriteFile(fh, (LPSTR)lpbi, dwDIBSize, &dwWritten, NULL);
    //清除
    GlobalUnlock(hDib);
    GlobalFree(hDib);
    CloseHandle(fh);

    return TRUE;
}