Direct2D (20) : 圖層之 TD2D1LayerParameters.opacityBrush (為圖層指定蒙版畫刷)

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);  {建立線性漸層畫刷}  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);  {在圖層中繪製映像}  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;

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