Direct2D (12) : 画刷之 ID2D1RadialGradientBrush

uses Direct2D, D2D1;



procedure TForm1.FormPaint(Sender: TObject);

var

  cvs: TDirect2DCanvas;

  iBrush: ID2D1RadialGradientBrush;

  R: TRect;

  rRGBP: TD2D1RadialGradientBrushProperties; //结构包含：中心点、偏移点、横向半径、纵向半径

  arrGradientStop: array[0..1] of TD2D1GradientStop;

  iGradientStops: ID2D1GradientStopCollection;

begin

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



  R := ClientRect;

  InflateRect(R, -ClientWidth div 6, -ClientHeight div 6);



  rRGBP.center := D2D1PointF(ClientWidth / 2, ClientHeight / 2);

  rRGBP.gradientOriginOffset := D2D1PointF(0, 0);

  rRGBP.radiusX := (R.Right - R.Left) / 2;

  rRGBP.radiusY := (R.Bottom - R.Top) / 2;



  arrGradientStop[0].position := 0.0;

  arrGradientStop[0].color := D2D1ColorF(clYellow);

  arrGradientStop[1].position := 1.0;

  arrGradientStop[1].color := D2D1ColorF(clRed);



  cvs.RenderTarget.CreateGradientStopCollection(

    @arrGradientStop[0], Length(arrGradientStop), D2D1_GAMMA_2_2, D2D1_EXTEND_MODE_CLAMP, iGradientStops

  );



  cvs.RenderTarget.CreateRadialGradientBrush(rRGBP, nil, iGradientStops, iBrush);

  cvs.Brush.Handle := iBrush;



  cvs.Pen.Width := 0;

  cvs.BeginDraw;

  cvs.Ellipse(R);

  cvs.EndDraw;

  cvs.Free;

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;

---

效果图：

---