画箭头

draw an arrow?

procedure ZeichnePfeil(I: TImage; P1, P2: TPoint);

 //created by Christof Urbaczek

 function GetDEG(Winkel: Extended): Extended; // gibt den Winkel im Gradma ß an

 begin

   Result := (Winkel * 2 * Pi) / 360;

 end;

 function GetRAD(Winkel: Extended): Extended; // gibt den Winkel im Winkelmaß an

 begin

   Result := (Winkel * 360) / (2 * Pi);

 end;

const

 s    = 10; // Seitenlänge der Pfeilspitze

 Beta = 50; // Spannwinkel der Pfeilspitze

var

 Punkte: array [0..2] of TPoint; // Array für die Punkte der Pfeilspitze

 Alpha, AlphaZ: Extended;        // Winkel zur horizontalen Achse durch P1

begin

 //Linie zeichnen

 I.Canvas.Brush.Color := clBlack;

 I.Canvas.Pen.Style   := psSolid;

 I.Canvas.MoveTo(P1.X, P1.Y);

 I.Canvas.LineTo(P2.X, P2.Y);

 //Pfeilspitze (1.Punkt)

 Punkte[0].X := P2.X;

 Punkte[0].Y := P2.Y;

 //Winkel ermitteln

 Alpha := 0;

 if P2.X = P1.X then

   AlphaZ := 0

 else

   AlphaZ := GetRAD(ArcTan((P2.Y - P1.Y) / (P2.X - P1.X)));

 if (P2.X > P1.X) and (P2.Y = P1.Y) then Alpha := 0          

 else if (P2.X > P1.X) and (P2.Y < P1.Y) then Alpha := 0 - AlphaZ

 else if (P2.X = P1.X) and (P2.Y < P1.Y) then Alpha := 90          

 else if (P2.X < P1.X) and (P2.Y < P1.Y) then Alpha := 180 - AlphaZ

 else if (P2.X < P1.X) and (P2.Y = P1.Y) then Alpha := 180          

 else if (P2.X < P1.X) and (P2.Y > P1.Y) then Alpha := 180 - AlphaZ

 else if (P2.X = P1.X) and (P2.Y > P1.Y) then Alpha := 270          

 else if (P2.X > P1.X) and (P2.Y > P1.Y) then Alpha := 360 - AlphaZ;

 //2.Punkt

 Punkte[1].X := round(P2.X - s * cos(GetDEG(Alpha - Beta div 2)));

 Punkte[1].Y := round(P2.Y + s * sin(GetDEG(Alpha - Beta div 2)));

 //3.Punkt

 Punkte[2].X := round(P2.X - s * cos(GetDEG(Alpha + Beta div 2)));

 Punkte[2].Y := round(P2.Y + s * sin(GetDEG(Alpha + Beta div 2)));

 //Pfeil zeichnen

 I.Canvas.Brush.Color := clBlack;

 I.Canvas.Polygon(Punkte);

end;

// einfacher Aufruf

procedure TForm1.Button1Click(Sender: TObject);

begin

 ZeichnePfeil(Image1, Point(20,20), Point(100,150));

end;