Direct2D (25) : 将画笔线条所占用的区域转换为路径 ID2D1Geometry.Widen()

uses Direct2D, D2D1;

procedure TForm1.FormPaint(Sender: TObject);
var
  cvs: TDirect2DCanvas;
  iGeometry: ID2D1Geometry;
  iPathGeometry: ID2D1PathGeometry;
  iGeometrySink: ID2D1GeometrySink;
begin
  {建立一个几何对象 iGeometry}
  D2DFactory.CreateEllipseGeometry(
    D2D1Ellipse(D2D1PointF(ClientWidth/2, ClientHeight/2), ClientWidth/4, ClientHeight/4),
    ID2D1EllipseGeometry(iGeometry)
  );

  cvs := TDirect2DCanvas.Create(Canvas, ClientRect);
  cvs.BeginDraw;

  {绘制 iGeometry}
  cvs.Pen.Color := clYellow;
  cvs.Pen.Width := 25;
  cvs.DrawGeometry(iGeometry);

  {创建 iPathGeometry，并把 iGeometry 的线条所占用的区域转换成新的路径到 iPathGeometry}
  D2DFactory.CreatePathGeometry(iPathGeometry);
  iPathGeometry.Open(iGeometrySink);
  iGeometry.Widen(25, nil, TD2DMatrix3x2F.Identity, 0, iGeometrySink); //参数4是曲直容差，效果图中包含把它设为 9 的演示
  iGeometrySink.Close;

  {绘制 iPathGeometry}
  cvs.Pen.Color := clRed;
  cvs.Pen.Width := 1;
  cvs.DrawGeometry(iPathGeometry);

  cvs.EndDraw;
  cvs.Free;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
  Repaint;
end;

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效果图：

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