截取當前的視窗(不是全螢幕)

procedure TForm1.Button1Click(Sender: TObject);
var
  HWND:THandle;
  dc:HDC ;
  rect:TRect ;
  dest:TBitmap;
  jpg :TJpegImage;
  w, h : integer;
begin
  HWND:=handle;
  GetWindowRect(HWND,rect);
  dc:=GetWindowDC(HWND);
  dest := TBitmap.Create;
  jpg :=  TJpegImage.create;
  w := rect.Right-rect.Left;
  h := rect.Bottom-rect.Top;
  dest.Width := w;
  dest.height := h;
  try
    BitBlt(dest.canvas.handle,0,0,w,h,dc,0,0,SRCCOPY );
    jpg.Assign(dest);
    jpg.CompressionQuality:=100;
    jpg.JPEGNeeded;
    jpg.Compress;
    jpg.SaveToFile('c:\1.jpg');
  finally
    ReleaseDC(HWND,dc);
    jpg.free;
    dest.Free;
  end;
end;