WriteableBitmap形状渲染

Question

我正在尝试在Silverlight中渲染一些Shape对象（Line，Rectangle），而我正在使用WriteableBitmap.Render（myShape，transform）。问题是Render函数似乎缺少抗锯齿功能。我错过了什么，或者使用WriteableBitmap这是不可能的？

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        bmp = new WriteableBitmap(800, 600);
        testImage.Source = bmp;
        line = new Line() { X1 = 10, X2 = 500, Y1 = 10, Y2 = 300 };
        line.Stroke = new SolidColorBrush(Colors.Red);
        line.StrokeStartLineCap = PenLineCap.Round;
        line.StrokeEndLineCap = PenLineCap.Round;
        line.StrokeLineJoin = PenLineJoin.Round;
        line.StrokeThickness = 1;
        CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);
    }

    private void CompositionTarget_Rendering(object sender, EventArgs e)
    {
        bmp.Render(line, line.GeometryTransform);
        bmp.Invalidate();
    }