关于打印图象大小的问题？(100分)

procedure TMainForm.printClick(Sender: TObject);
var
   ScaleX, ScaleY: Integer;
   R: TRect;

begin
   if printdialog1.Execute then
      begin
         Printer.BeginDoc; // **
         with Printer do
         try
            ScaleX := GetDeviceCaps(Handle, logPixelsX) div
               PixelsPerInch;
            ScaleY := GetDeviceCaps(Handle, logPixelsY) div
               PixelsPerInch;
            R := Rect(0, 0, Image1.Picture.Width * ScaleX,
               .Image1.Picture.Height * ScaleY);
            Canvas.StretchDraw(R, Image1.Picture.Graphic); // ** 要拉伸
         finally
            EndDoc; // **
         end;
      end;
end;