unit Unit1;

interface

uses
   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
   System.Classes, Vcl.Graphics, Math,
   Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls;

type
   TMatrix = array[0..3] of array[0..3] of Integer;

   TForm1 = class(TForm)
      imgDrawPlace: TImage;
      procedure FormCreate(Sender: TObject);
   private
      procedure DrawCircle(const Value, Radius: Integer; const Pos: TPoint);
      procedure DrawLine(const FPoint, SPoint: TPoint);
      procedure DrawArrow( FPoint, SPoint: TPoint);
      procedure DrawGraph(const AdjacentMatrix: TMatrix; const CentrePoint: TPoint);

      function  CountSecontPointPosByAngle(const Angle, Linelen: integer;
         const FPoint: TPoint): TPoint;
   public
      { Public declarations }
   end;

const
   NodeRadius = 20;
   PenWidth = 2;
   PenArrowWidth = 7;


var
   Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.DrawCircle(const Value, Radius: Integer; const Pos: TPoint);
var
   XTextOffset, YTextOffset: integer;
begin
   XTextOffset := (Radius div 5);
   YTextOffset := (Radius div 5) + 5;

   imgDrawPlace.Canvas.Pen.Width := PenWidth;
   imgDrawPlace.Canvas.Ellipse((Pos.X - Radius), (Pos.Y - Radius),
                               (Pos.X + Radius), (Pos.Y + Radius));
   imgDrawPlace.Canvas.Font.Size := 13;
   imgDrawPlace.Canvas.TextOut(Pos.X - XTextOffset, Pos.Y - YTextOffset, IntToStr(Value));
end;

procedure TForm1.DrawLine(const FPoint, SPoint: TPoint);
begin
   imgDrawPlace.Canvas.MoveTo(FPoint.X, FPoint.Y);
   imgDrawPlace.Canvas.LineTo(SPoint.X, SPoint.Y);
end;

procedure TForm1.DrawArrow(FPoint, SPoint: TPoint);
const
   ArrowLenCoefficient = 8;
var
   OldPenWidth: Integer;
   XOffset, YOffset: Integer;
begin
   DrawLine(FPoint, SPoint);

   OldPenWidth := imgDrawPlace.Canvas.Pen.Width;
   imgDrawPlace.Canvas.Pen.Width :=  PenArrowWidth;

   XOffset := Abs(FPoint.X - SPoint.X) div ArrowLenCoefficient;
   YOffset := Abs(FPoint.Y - SPoint.Y) div ArrowLenCoefficient;

   if Max(FPoint.X, SPoint.X) = SPoint.X then
      FPoint.X :=  SPoint.X - XOffset
   else
      FPoint.X :=  SPoint.X + XOffset;


   if Max(FPoint.Y, SPoint.Y) = SPoint.Y then
      FPoint.Y :=  SPoint.Y - YOffset
   else
      FPoint.Y :=  SPoint.Y + YOffset;

   DrawLine(FPoint, SPoint);
   imgDrawPlace.Canvas.Pen.Width := OldPenWidth;
end;

procedure TForm1.FormCreate(Sender: TObject);
const
   START_MATRIX2: TMatrix =
   ((0, 10, 6,  0),
    (10, 0, 0,   0),
    (10, 10, 0,   10),
    (0, 0,   0,   0));
var
   FPoint, a: TPoint;
begin
   FPoint.X := 300;
   FPoint.Y := 300;

   DrawGraph(START_MATRIX2, FPoint);
end;


procedure TForm1.DrawGraph(const AdjacentMatrix: TMatrix; const CentrePoint: TPoint);
var
   CurAngle, AngleOffset, i, j, AdjacentMatrixLen: Integer;
   CurNodePos: TPoint;
   NodesPositions: array of TPoint;
begin
   AdjacentMatrixLen := Length(AdjacentMatrix);

   AngleOffset := (360 div AdjacentMatrixLen);
   SetLength(NodesPositions, AdjacentMatrixLen);
   CurAngle := 0;

   for i := 0 to High(AdjacentMatrix) do
   begin
      NodesPositions[i] := CountSecontPointPosByAngle(CurAngle, 200, CentrePoint);
      Inc(CurAngle, AngleOffset);
   end;

   for i := 0 to High(AdjacentMatrix) do
      for j := 0 to High(AdjacentMatrix) do
         if AdjacentMatrix[i, j] <> 0 then
            DrawArrow(NodesPositions[i], NodesPositions[j]);

   for i := 0 to High(NodesPositions) do
      DrawCircle(i+1, NodeRadius, NodesPositions[i]);
end;



function TForm1.CountSecontPointPosByAngle(const Angle, Linelen: integer;
   const FPoint: TPoint): TPoint;
begin
   Result.X := FPoint.X + Round(Linelen * Cos(Angle * Pi / 180));
   Result.Y := FPoint.Y - Round(Linelen * Sin(Angle * Pi / 180));
end;

end.