Direct2D (28) : 获取几何图形的面积、线总长度和指定位置的点坐标

uses Direct2D, D2D1;



procedure TForm1.FormPaint(Sender: TObject);

var

  cvs: TDirect2DCanvas;

  iEllipseGeometry: ID2D1EllipseGeometry;

  area,length: Single;

  rPointF1,rPointF2: TD2DPoint2f;

  ptCenter: TPoint;

begin

  ptCenter := Point(ClientWidth div 2, ClientHeight div 2);

  D2DFactory.CreateEllipseGeometry(D2D1Ellipse(ptCenter, ClientWidth/4, ClientHeight/4), iEllipseGeometry);



  {获取面积与周长}

  iEllipseGeometry.ComputeArea(TD2DMatrix3x2F.Identity, 0, area);

  iEllipseGeometry.ComputeLength(TD2DMatrix3x2F.Identity, 0, length);



  {获取图形的起始处和 1/4 处的点}

  iEllipseGeometry.ComputePointAtLength(0, TD2DMatrix3x2F.Identity, 0, @rPointF1, nil);

  iEllipseGeometry.ComputePointAtLength(length/4, TD2DMatrix3x2F.Identity, 0, @rPointF2, nil);



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

  cvs.BeginDraw;

  cvs.RenderTarget.Clear(D2D1ColorF(clWhite));



  cvs.Font.Size := 9;

  cvs.TextOut(5, 5, Format('面积: %f; 周长: %f', [area, length]));



  cvs.DrawGeometry(iEllipseGeometry);



  cvs.MoveTo(ptCenter.X, ptCenter.Y);

  cvs.LineTo(Trunc(rPointF1.x), Trunc(rPointF1.y));

  cvs.MoveTo(ptCenter.X, ptCenter.Y);

  cvs.LineTo(Trunc(rPointF2.x), Trunc(rPointF2.y));



  cvs.EndDraw;

  cvs.Free;

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;

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效果图：

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