如何在Delphi中截取Active Window的截图？

uses
  Winapi.Windows, Winapi.GDIPAPI, Winapi.GDIPOBJ, System.SysUtils, System.Classes, Vcl.Graphics;

function CaptureScreen(hWnd: HWND): TBitmap;
var
  DC: HDC;
  rc: TRect;
begin
  Result := TBitmap.Create;
  try
    GetWindowRect(hWnd, rc);
    Result.Width := rc.Right - rc.Left;
    Result.Height := rc.Bottom - rc.Top;
    DC := GetWindowDC(hWnd);
    try
      Result.Canvas.CopyRect(Rect(0, 0, Result.Width, Result.Height),
        TCanvas.Create, Rect(0, 0, Result.Width, Result.Height));
    finally
      ReleaseDC(hWnd, DC);
    end;
  except
    Result.Free;
    raise;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  hWnd: HWND;
  bmp: TBitmap;
begin
  hWnd := GetForegroundWindow;
  bmp := CaptureScreen(hWnd);
  try
    Image1.Picture.Assign(bmp);
  finally
    bmp.Free;
  end;
end;