Линии по алгоритму Брезенхема

unit uzd1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls;
 
type
  TForm1 = class(TForm)
    Image1: TImage;
    procedure FormCreate(Sender: TObject);
    procedure Brezenhem(x1,y1,x2,y2:integer);
    procedure Image1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Brezenhem(x1, y1, x2, y2: integer);
var Pn,dx,dy,xn,yn,xi,yi:integer;
begin
 xn:=x1;
 yn:=y1;
 dx:=abs(x2-x1);
 dy:=abs(y2-y1);
 if x1<x2 then xi:=1 else xi:=-1;
 if y1<y2 then yi:=1 else yi:=-1;
 if dx>dy then
 begin
  Pn:=2*dy-dx;
  while xn<>x2 do
   begin
    if  Pn>0 then
     begin
      xn:=xn+xi;
      yn:=yn+yi;
      Pn:=Pn+2*dy-2*dx;
     end
      else
       begin
         xn:=xn+xi;
         Pn:=Pn+2*dy;
       end;
      image1.Canvas.Pixels[xn,yn]:=clBlack;
   end;
 
 end;
 
 
 
end;
 
procedure TForm1.FormCreate(Sender: TObject);
begin
 image1.Canvas.Moveto(0,image1.Height div 2);
 image1.Canvas.LineTo(image1.Width,image1.Height div 2);
 image1.Canvas.MoveTo(image1.Width div 2,0);
 image1.Canvas.LineTo(image1.Width div 2,image1.Height);
 
end;
 
procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Brezenhem(image1.Width div 2,
            image1.Height div 2,
            X,Y);
end;
 
end.