c++ - Convert PrintWindow to BitBlt to capture screenshot of a specific window -

i have c++ program capture screenshot of specific window , save using following code

 int main()  {    gdiplusstartupinput gdiplusstartupinput;    ulong_ptr gdiplustoken;    gdiplusstartup(&gdiplustoken, &gdiplusstartupinput, null);     rect rc;    hwnd hwnd = findwindow(null,text("window title here"));    if(hwnd == null)    {       cout<<"can't find window";       return 0;    }      getclientrect(hwnd,&rc);      hdc hdcscreen = getdc(null);     hdc hdc = createcompatibledc(hdcscreen);      hbitmap hbmp = createcompatiblebitmap(hdcscreen,rc.right - rc.left,rc.bottom - rc.top);      selectobject(hdc,hbmp);      printwindow(hwnd,hdc,null);      bitmaptojpg(hbmp,rc.right - rc.left,rc.bottom-rc.top); //function convert hbmp bitmap jpg      deletedc(hdc);     deleteobject(hbmp);     releasedc(null,hdcscreen);  } 

this code works many of windows, of windows, output black image correct width , height. on searching found solution use bitblt(). cannot figure out how replace printwindow() bitblt() , output hbitmap. need

first, replace hdcscreen hdcwnd, getdc(hwnd) instead of getdc(null). won't change anything, more adequate, printwindow().
then, replace :

printwindow(hwnd,hdc,null); 

by :

bitblt( hdc, 0, 0, rc.right - rc.left,rc.bottom-rc.top, hdcwnd, 0, 0, srccopy );