WPF binding visual of user control and window

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C#

XAML

WPF

Hi. As i am trying to make one thing i need help with binding.
So, i have a user-control and a window. User control represents an ellipse with blurred image as ellipse fill and image with increased contrast as ellipse stroke.
User control source:

<Border x:Name="src" removed="Silver">
    <Image Source="http://cs322217.vk.me/v322217001/8ceb/83F7vjpflls.jpg" Stretch="UniformToFill"></Image>
</Border>
<Border Margin="40">
    <Grid>
		<Ellipse>
			<Ellipse.Effect>
				<effects:BrightContrastEffect Brightness="0" Contrast="0.7"></effects:BrightContrastEffect>
            </Ellipse.Effect>
            <Ellipse.Fill>
				<VisualBrush Visual="{Binding ElementName=src}" Stretch="None"></VisualBrush>
			</Ellipse.Fill>
            </Ellipse>
            <Ellipse Margin="10">
                <Ellipse.BitmapEffect>
                    <BlurBitmapEffect Radius="20" x:Name="blur"></BlurBitmapEffect>
                </Ellipse.BitmapEffect>
                <Ellipse.Fill>
                    <VisualBrush Visual="{Binding ElementName=src}" Stretch="None"></VisualBrush>
                </Ellipse.Fill>
			</Ellipse>
        </Ellipse>
    </Grid>
</Border>

Window:

<Grid>
	<my:control></my:control>
</Grid>

and i have this result: image of result[^]
this is the effect what i need.
But. How i can achieve the same effect, if i set the image in window:

<Grid>
	<Grid.Background>
		<ImageBursh ImageSource="http://cs322217.vk.me/v322217001/8ceb/83F7vjpflls.jpg" Stretch="UniformToFill"></Image>
	</Grid.Background>
	<my:control></my:control>
</Grid>

and will remove

<Border x:Name="src" removed="Silver">
    <Image Source="http://cs322217.vk.me/v322217001/8ceb/83F7vjpflls.jpg" Stretch="UniformToFill"></Image>
</Border>

from user control.
I DO NOT need this[^]. I need blurred part of image to fit the original image on window, i mean in position and scaling.
any ideas?