procedure GetScreenShot(var ABitmap : TBitmap);
var
  DC : THandle;
begin
  if Assigned(ABitmap) then
  begin
    DC := GetDC(0);
    try
      ABitmap.Width := Screen.Width;
      ABitmap.Height := Screen.Height;
      BitBlt(ABitmap.Canvas.Handle,
             0,0,Screen.Width,Screen.Height,
             DC,
             0,0,
             SrcCopy
        );
    finally
      ReleaseDC(0, DC);
    end;
  end;
end;