抓取屏幕并压缩生成HBITMAP

 HBITMAP GetScreenBmp()
 {
     HWND hwnd = ::GetDesktopWindow();
     HDC hsrc = ::GetDC(hwnd);
     HDC hmemdc = ::CreateCompatibleDC(hsrc);
     RECT rc; ::GetWindowRect(hwnd,&rc);
     SIZE sz;sz.cx=rc.right-rc.left;sz.cy=rc.bottom-rc.top;
     HBITMAP hbmp = ::CreateCompatibleBitmap(hsrc,sz.cx,sz.cy);
     HGDIOBJ holdbmp = ::SelectObject(hmemdc,hbmp);
     ::BitBlt(hmemdc,,,sz.cx,sz.cy,hsrc,rc.left,rc.top,SRCCOPY);
     ::SelectObject(hmemdc,holdbmp);
     ::DeleteObject(hmemdc);
     ::ReleaseDC(hwnd,hsrc);
     return hbmp;
 }