vc++/mfc截图 保存和显示

## 1. 实现截图程序的api接口 ##

HBITMAP CaptureScreen(LPRECT lpRect)//lpRect为NULL时表示全屏幕截图
{
    HDC      hdc, hdcMem ;
    HBITMAP  hemfCopy ;
    HWND     hwndScr ;
    int      dstcx, dstcy ;
    if(lpRect)
    {
        dstcx = lpRect->right - lpRect->left ;
        dstcy = lpRect->bottom - lpRect->top ;
    }
    else
    {
        dstcx = GetSystemMetrics(SM_CXSCREEN) ;
        dstcy = GetSystemMetrics(SM_CYSCREEN) ;
    }
    if (LockWindowUpdate(hwndScr = GetDesktopWindow ()))
    {
        hdc  = GetDCEx (hwndScr, NULL, DCX_CACHE | DCX_LOCKWINDOWUPDATE) ;
        hdcMem = CreateCompatibleDC (hdc) ;
        if(NULL==hdcMem)
        {
            ReleaseDC (hwndScr, hdc) ;
            LockWindowUpdate (NULL) ;
            return NULL;
        }
        hemfCopy = CreateCompatibleBitmap (hdc, abs(dstcx), abs(dstcy)) ;
        if(NULL==hemfCopy)
        {
            DeleteDC (hdcMem) ;
            ReleaseDC (hwndScr, hdc) ;
            LockWindowUpdate (NULL) ;
            return NULL;
        }
        SelectObject (hdcMem, hemfCopy) ;
        if(lpRect)
            StretchBlt (hdcMem, 0, 0, abs(dstcx), abs(dstcy), 
            hdc, lpRect->left, lpRect->top, dstcx, dstcy, SRCCOPY|CAPTUREBLT) ;
        else
            BitBlt (hdcMem, 0, 0, dstcx, dstcy, 
            hdc, 0, 0, SRCCOPY|CAPTUREBLT) ;
        DeleteDC (hdcMem) ;
        ReleaseDC (hwndScr, hdc) ;
        LockWindowUpdate (NULL) ;
        return hemfCopy;
    }
    return NULL;
}
``

2、保存图片

BOOL SaveBmp(HBITMAP hBitmap,CString FileName)         
{         
    HDC     hDC;         
    //当前分辨率下每象素所占字节数         
    int     iBits;         
    //位图中每象素所占字节数         
    WORD     wBitCount;         
    //定义调色板大小，     位图中像素字节大小     ，位图文件大小     ，     写入文件字节数             
    DWORD     dwPaletteSize=0,   dwBmBitsSize=0,   dwDIBSize=0,   dwWritten=0;             
    //位图属性结构             
    BITMAP     Bitmap;                 
    //位图文件头结构         
    BITMAPFILEHEADER     bmfHdr;                 
    //位图信息头结构             
    BITMAPINFOHEADER     bi;                 
    //指向位图信息头结构                 
    LPBITMAPINFOHEADER     lpbi;                 
    //定义文件，分配内存句柄，调色板句柄             
    HANDLE     fh,   hDib,   hPal,hOldPal=NULL;             

    //计算位图文件每个像素所占字节数             
    hDC  = CreateDC(TEXT("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;         

    //为位图内容分配内存             
    hDib  = GlobalAlloc(GHND,dwBmBitsSize+dwPaletteSize+sizeof(BITMAPINFOHEADER));             
    lpbi  = (LPBITMAPINFOHEADER)GlobalLock(hDib);             
    *lpbi  = bi;             

    //     处理调色板                 
    hPal  = GetStockObject(DEFAULT_PALETTE);             
    if (hPal)             
    {             
        hDC  = ::GetDC(NULL);             
        hOldPal = ::SelectPalette(hDC,(HPALETTE)hPal, FALSE);             
        RealizePalette(hDC);             
    }         

    //     获取该调色板下新的像素值             
    GetDIBits(hDC,hBitmap, 0,(UINT)Bitmap.bmHeight,  
        (LPSTR)lpbi+ sizeof(BITMAPINFOHEADER)+dwPaletteSize,   
        (BITMAPINFO *)lpbi, DIB_RGB_COLORS);             

    //恢复调色板                 
    if (hOldPal)             
    {             
        ::SelectPalette(hDC,   (HPALETTE)hOldPal,   TRUE);             
        RealizePalette(hDC);             
        ::ReleaseDC(NULL,   hDC);             
    }             

    //创建位图文件                 
    fh  = CreateFile(FileName,   GENERIC_WRITE,0,   NULL,   CREATE_ALWAYS,           
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,   NULL);             

    if (fh     ==  INVALID_HANDLE_VALUE)         return     FALSE;             

    //     设置位图文件头             
    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;             
    //     写入位图文件头             
    WriteFile(fh,   (LPSTR)&bmfHdr,   sizeof(BITMAPFILEHEADER),   &dwWritten,   NULL);             
    //     写入位图文件其余内容             
    WriteFile(fh,   (LPSTR)lpbi,   dwDIBSize,   &dwWritten,   NULL);             
    //清除                 
    GlobalUnlock(hDib);             
    GlobalFree(hDib);             
    CloseHandle(fh);             

    return     TRUE;         
}  

3、在dialog中 显示

在onPaint中显示 ，其中mfc设计到 BITMAP hbitmap和cbitmap之间的关系
在mfc程序中，使用cbitmap

        CPaintDC dc(this);

        CDC dcimage;
        CBitmap bkg;
        bkg.Attach(g_bitmap);
        BITMAP bkginfo;
        bkg.GetBitmap(&bkginfo);//获取位图信息

        dcimage.CreateCompatibleDC(&dc);
        dcimage.SelectObject(&bkg);

//      dc.BitBlt(0,0,nWidth,nHeight,&dcimage,0,0,SRCCOPY);

        dc.StretchBlt(0,0,nWidth,nHeight,&dcimage,0,0,bkginfo.bmWidth,bkginfo.bmHeight,SRCCOPY);

`