How do I avoid an OutOfMemoryException when using DropShadowEffect?

When a DropShadowEffect is added, zooming in with ScaleTransform needs a lot of memory. Too much memory! Without the DropShaddowEffect, there's no problem.

I do not understand, why it is leaking memory and what I could do to work around.

Here's the code for a simple test program:

XAML

<Grid>
  <Grid.RowDefinitions>
    <RowDefinition />
    <RowDefinition Height="20"/>
  </Grid.RowDefinitions>
  <Canvas x:Name="canvas" Height="100" Width="100"
          Background="Beige" Grid.Row="0">
    <Canvas.RenderTransform>
      <ScaleTransform ScaleX="{Binding ElementName=slide, Path=Value}"
                      ScaleY="{Binding ElementName=slide, Path开发者_Python百科=Value}" />
    </Canvas.RenderTransform>
  </Canvas>
  <Grid Grid.Row="1">
    <Slider x:Name="slide" Minimum="1" Maximum="200"/>
  </Grid>
</Grid>

CodeBehind:

var dropShadowEffect = new DropShadowEffect();
canvas.Effect = dropShadowEffect;

You should read this blog: http://youpvp.com/blog/post/What-you-need-to-know-about-DropShadow-to-create-great-Silverlight-applications.aspx

Pretty much the memory usage you see is in line with that should be expected. Shadow for 500x500 pixels canvas (5x zoom in your case) would take >1MB memory. Bigger shadow will take even more.

Is this .net 3.5 or 4.0? With 3.5 the drop shadow effect should be avoided to due rendering issues with it.

http://joshsmithonwpf.wordpress.com/2007/07/24/a-lightweight-alternative-to-dropshadowbitmapeffect/