Kreisbogen direkt zeichnen (ohne canvas.arc)

[toms]

Hallo,

Falls du English kannst, lies dir doch mal den Artikel Draw an Arc with ActionScript durch.

Die Delphi Umsetzung würde etwa so aussehen:

Delphi-Quellcode:

procedure drawArc(Canvas: TCanvas; centerX, centerY, radius, startAngle, arcAngle: Real; steps: Word);
var
  angleStep, angle, twoPI, xx, yy: Real;
  i: Word;
begin
 //
 // For convenience, store the number of radians in a full circle.
  twoPI := 2 * PI;
 //
 // To determine the size of the angle between each point on the
 // arc, divide the overall angle by the total number of points.
  angleStep := arcAngle / steps;
 //
 // Determine coordinates of first point using basic circle math.
  xx := centerX + cos(startAngle * twoPI) * radius;
  yy := centerY + sin(startAngle * twoPI) * radius;
 //
 // Move to the first point.
  Canvas.moveTo(Trunc(xx), Trunc(yy));
 //
 // Draw a line to each point on the arc.
  for i := 1 to steps - 1 do
  begin
  //
  // Increment the angle by "angleStep".
    angle := startAngle + i * angleStep;
  //
  // Determine next point's coordinates using basic circle math.
    xx := centerX + cos(angle * twoPI) * radius;
    yy := centerY + sin(angle * twoPI) * radius;
  //
  // Draw a line to the next point.
    Canvas.lineTo(Trunc(xx), Trunc(yy));
  end;
end;


procedure TForm1.Button1Click(Sender: TObject);
begin
  drawArc(Canvas, 250, 250, 200, 45 / 360, -90 / 360, 20);
end;