Direct2D (20) : 图层之 TD2D1LayerParameters.opacityBrush (为图层指定蒙版画刷)

uses Direct2D, D2D1;



procedure TForm1.FormPaint(Sender: TObject);

var

  cvs: TDirect2DCanvas;

  iLayer: ID2D1Layer;

  rLayerParameters: TD2D1LayerParameters;

  wic: TWICImage;

  R: TRect;

  iLinearGradientBrush: ID2D1LinearGradientBrush;

  rLinear: TD2D1LinearGradientBrushProperties;

  arrGradientStop: array[0..2] of TD2D1GradientStop;

  iGradientStops: ID2D1GradientStopCollection;

begin

  wic := TWICImage.Create;

  wic.LoadFromFile('C:\Temp\Test.png');

  R := Rect(0, 0, wic.Width, wic.Height);

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



  {建立线性渐变画刷}

  rLinear.startPoint := D2D1PointF(0, 0);

  rLinear.endPoint := D2D1PointF(0, wic.Height);

  arrGradientStop[0].position := 0.0;

  arrGradientStop[0].color := D2D1ColorF(clBlack, 1.0);

  arrGradientStop[1].position := 0.6;

  arrGradientStop[1].color := D2D1ColorF(clWhite, 0.0);

  arrGradientStop[2].position := 1.0;

  arrGradientStop[2].color := D2D1ColorF(clBlack, 1.0);

  cvs.RenderTarget.CreateGradientStopCollection(@arrGradientStop[0], Length(arrGradientStop), D2D1_GAMMA_2_2, D2D1_EXTEND_MODE_CLAMP, iGradientStops);

  cvs.RenderTarget.CreateLinearGradientBrush(rLinear, nil, iGradientStops, iLinearGradientBrush);



  cvs.RenderTarget.SetTransform(TD2DMatrix3x2F.Translation((ClientWidth-wic.width)/2, (ClientHeight-wic.height)/2));

  cvs.BeginDraw;

  cvs.Brush.Color := clBlack;

  cvs.Rectangle(R);



  {在图层中绘制图像}

  cvs.RenderTarget.CreateLayer(nil, iLayer);

  rLayerParameters.contentBounds := R;

  rLayerParameters.geometricMask := nil;

  rLayerParameters.maskAntialiasMode := D2D1_ANTIALIAS_MODE_PER_PRIMITIVE;

  rLayerParameters.maskTransform := TD2DMatrix3x2F.Identity;

  rLayerParameters.opacity := 1.0;

  rLayerParameters.opacityBrush := iLinearGradientBrush; //!

  rLayerParameters.layerOptions := D2D1_LAYER_OPTIONS_NONE;

  cvs.RenderTarget.PushLayer(rLayerParameters, iLayer);

  cvs.StretchDraw(R, wic);

  cvs.RenderTarget.PopLayer;



  cvs.EndDraw;

  cvs.Free;

  wic.Free;

end;



procedure TForm1.FormResize(Sender: TObject);

begin

  Repaint;

end;

---

效果图：

---