How to display SkeletonStream on a DepthStream or ColorStream Kinect Wpf

I would like to know how to overlay two Image objects in Wpf. I've made two streams which output a video, one for bones and another just a normal video. Now I would like to add them together, so the skeleton would be displayed on the color video. A part of my XAML code is

<Grid Name="layoutGrid">
    <Grid Name="VideoGrid" ClipToBounds="True" Background="AliceBlue">
        <Image Name="ColorImage" Width="640" Height="480"/>
        <Image Name="SkeletalImage" Width="640" Height="480"/>

        <Canvas Background="Transparent"/>
    </Grid>
    <StatusBar VerticalAlignment="Bottom" HorizontalAlignment="Center">
        <Button Name="Button1" Content="Skeleton Only" Width="120"/>
    </StatusBar>
</Grid>

When I do this, only the Skeletal image is displayed and if I switch the both Images then the color image is shown. It seems like Canvas background doesn't do the trick (to make the black part of skeletal image transparent)

Solution

I thought the problem was in my XAML code but it was actually at drawing the transparent background to set the render size. The background for skeleton image was black

dc.DrawRectangle(Brushes.Black, null, 
                  new Rect(0.0, 0.0, RenderWidth, RenderHeight));

instead of transparent

dc.DrawRectangle(Brushes.Transparent, null, 
                  new Rect(0.0, 0.0, RenderWidth, RenderHeight));

that fixed my problem. Thanks though