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;

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效果图：

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