Windows下截屏保存到内存及其BMP

    HWND hWnd = ::GetDesktopWindow();//获得屏幕的HWND.
    HDC hScreenDC = ::GetDC(hWnd);   //获得屏幕的HDC.
    HDC MemDC = ::CreateCompatibleDC(hScreenDC);
    RECT rect;
    ::GetWindowRect(hWnd,&rect);
    SIZE screensize;
    screensize.cx=600;
    screensize.cy=400;
    //    hBitmap = ::CreateCompatibleBitmap(hScreenDC,screensize.cx,screensize.cy);
    HBITMAP hBitmap = ::CreateCompatibleBitmap(hScreenDC,screensize.cx,screensize.cy);//改成创建的幕布的大小。
    HGDIOBJ hOldBMP = ::SelectObject(MemDC,hBitmap);
    //    ::BitBlt(MemDC,0,0,screensize.cx,screensize.cy,hScreenDC,rect.left,rect.top,SRCCOPY);//by tang wei
    ::BitBlt(MemDC,0,0,screensize.cx,screensize.cy,hScreenDC,rect.left,rect.top,SRCCOPY);//改变截屏大小，从全屏改成
    ::SelectObject(MemDC,hOldBMP);
    ::DeleteObject(MemDC);

    ::ReleaseDC(hWnd,hScreenDC);

 ////////////////////////////////////////////////////////

 
    //by Tang Wei   直接以时间为名字保持截图
    SYSTEMTIME st;
    GetLocalTime(&st);
    new_filename.Format("%.2d-%.2d-%.2d",st.wHour,st.wMinute,st.wSecond);
     CString addr("data_bmp//");
    CString new_format1(".bmp");
    CString new_format2(".txt");
    CString new_name1 = addr + new_filename + new_format1;
    CString new_name2 = addr + new_filename + new_format2;
    UpdateData();
    WriteBmpToFile(hBitmap,new_name1,new_name2);

void CTestbmpcpDlg::WriteBmpToFile(HBITMAP hBitmap,CString strFileName1,CString strFileName2)
{
    HDC hDC =::CreateDC("DISPLAY",NULL,NULL,NULL);
    int iBits = ::GetDeviceCaps(hDC, BITSPIXEL) * ::GetDeviceCaps(hDC, PLANES);//当前分辨率下每个像素所占字节数  
    ::DeleteDC(hDC);

    WORD   wBitCount;   //位图中每个像素所占字节数    
    if (iBits <= 1)
        wBitCount = 1;
    else if (iBits <= 4)
        wBitCount = 4;
    else if (iBits <= 8)
        wBitCount = 8;
    else if (iBits <= 24)
        wBitCount = 24;
    else
        wBitCount = iBits;
            
    DWORD   dwPaletteSize=0;    //调色板大小， 位图中像素字节大小
    if (wBitCount <= 8)        
        dwPaletteSize = (1 << wBitCount) *    sizeof(RGBQUAD);    
    

    BITMAP  bm;        //位图属性结构
    ::GetObject(hBitmap, sizeof(bm), (LPSTR)&bm);  

    
    BITMAPINFOHEADER   bi,bi1;       //位图信息头结构     
    bi.biSize            = sizeof(BITMAPINFOHEADER);  
    bi.biWidth           = bm.bmWidth;
    bi.biHeight          = bm.bmHeight;
    bi.biPlanes          = 1;
    bi.biBitCount        = wBitCount;
    bi.biCompression     = BI_RGB; //BI_RGB表示位图没有压缩
    bi.biSizeImage       = 0;
    bi.biXPelsPerMeter   = 0;
    bi.biYPelsPerMeter   = 0;
    bi.biClrUsed         = 0;
    bi.biClrImportant    = 0;
    bi1=bi;
    bi1.biBitCount=24;
    
    DWORD dwBmBitsSize = ((bm.bmWidth * wBitCount+31)/32) * 4 * bm.bmHeight;   
    HANDLE hDib  = ::GlobalAlloc(GHND,dwBmBitsSize + dwPaletteSize + sizeof(BITMAPINFOHEADER));  //为位图内容分配内存
    LPBITMAPINFOHEADER lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDib);
    *lpbi = bi;
    
    HANDLE hPal = ::GetStockObject(DEFAULT_PALETTE);  // 处理调色板
    HANDLE  hOldPal=NULL;
    if (hPal)
    {
        hDC = ::GetDC(NULL);
        hOldPal = SelectPalette(hDC,(HPALETTE)hPal, FALSE);
        RealizePalette(hDC);
    }
    int nOutputBytes = 0;
    unsigned char *pJpp,*m_pDibBits;
    pJpp = new unsigned char [dwBmBitsSize];
    m_pDibBits = new unsigned char [dwBmBitsSize];
    //::GetDIBits(hDC, hBitmap, 0, (UINT) bm.bmHeight,m_pDibBits,(BITMAPINFO*)lpbi,DIB_RGB_COLORS);
    ::GetDIBits(hDC, hBitmap, 0, (UINT) bm.bmHeight,(LPSTR)lpbi + sizeof(BITMAPINFOHEADER)+dwPaletteSize,(BITMAPINFO*)lpbi,DIB_RGB_COLORS);// 获取该调色板下新的像素值
    if (hOldPal)//恢复调色板
    {
        SelectPalette(hDC, (HPALETTE)hOldPal, TRUE);
        RealizePalette(hDC);
        ::ReleaseDC(NULL, hDC);
    }
    memcpy(m_pDibBits,(LPSTR)lpbi+sizeof(BITMAPINFOHEADER)+dwPaletteSize,dwBmBitsSize); // by tang wei  m_pDibBits指向BMP的出去三个头部分后的实际数据
/*    int i=0,j=0;
    
    for(j=0;j<dwBmBitsSize;j++)
    {
        if(j%4==3)
            j++;
        m_pDibBits[i]=m_pDibBits[j];        
        i++;
    }*/

   
    BITMAPFILEHEADER   bmfHdr; //位图文件头结构     
    bmfHdr.bfType = 0x4D42;  // "BM"      // 设置位图文件头
    DWORD 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;
    
    HANDLE hFile = CreateFile(strFileName1, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);//创建位图文件   
    DWORD dwWritten;
    WriteFile(hFile, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten, NULL);    // 写入位图文件头
    WriteFile(hFile, (LPSTR)lpbi, dwDIBSize, &dwWritten, NULL);// 写入位图文件其余内容
    
    //By Tang Wei 同时把位图文件部分写到txt里面。
    //FILE* pFile;
    //pFile = fopen(strFileName2,"wb");
    //fwrite(m_pDibBits,dwBmBitsSize,1,pFile);
    ofstream outfile(strFileName2);
    int i;
    byte temp;
    int temp_int;
    for (i=0 ; i<dwBmBitsSize; i++)
    {
        temp = *(m_pDibBits+i);
        temp_int = temp;
        outfile<<temp_int<<' ';
    }
    //保存到内存
    char* BmpBuffer;
    BmpBuffer = new char [sizeof(BITMAPFILEHEADER) + dwDIBSize];
    memcpy(BmpBuffer,(LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER));
    memcpy(BmpBuffer+sizeof(BITMAPFILEHEADER),(LPSTR)lpbi, dwDIBSize);

    GlobalUnlock(hDib);   //清除   
    GlobalFree(hDib);
    CloseHandle(hFile);
    delete []pJpp;
    delete []m_pDibBits;
}