Ковёр Серпинского

unit Unit1; 
 
{$mode objfpc}{$H+}
 
interface
 
uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
  ExtCtrls;
 
type
 
  { TForm1 }
 
  TForm1 = class(TForm)
    Button1: TButton;
    PaintBox1: TPaintBox;
    procedure Button1Click(Sender: TObject);
  private
    { private declarations }
 
    procedure Serp( x1, y1, x2, y2: Real; n: Integer);
  public
    { public declarations }
  end; 
 
var
  Form1: TForm1; 
  x1, y1, x2, y2, x3, y3: Double;
 
implementation
 
{$R *.lfm}
 
{ TForm1 }
 
procedure TForm1.Serp(x1, y1, x2, y2: Real; n: Integer);
var
	x1n, y1n, x2n, y2n: Real;
 
begin
	if  n > 0  then
	begin
		x1n := 2*x1/3 + x2 / 3;
		x2n := x1/3 + 2*x2 / 3;
		y1n := 2*y1/3 + y2 / 3;
		y2n := y1/3+2*y2 / 3;
		PaintBox1.canvas.Rectangle(Round(x1n), Round(y1n), Round(x2n), Round(y2n));
		Serp(x1, y1, x1n, y1n, n-1);
		Serp(x1n, y1, x2n, y1n, n-1);
		Serp(x2n, y1, x2, y1n, n-1);
		Serp(x1, y1n, x1n, y2n, n-1);
		Serp(x2n, y1n, x2, y2n, n-1);
		Serp(x1, y2n, x1n, y2, n-1);
		Serp(x1n, y2n, x2n, y2, n-1);
		Serp(x2n, y2n, x2, y2, n-1)
	end
end;
 
 
procedure TForm1.Button1Click(Sender: TObject);
begin
   paintbox1.canvas.Rectangle(20, 20, 460, 460);
   Serp(20, 20, 460, 460, 4);
end;
 
end.