private double _time = 0.0;
 
private void Timer_Tick(object sender, EventArgs e)
{
    // increment phi and update the reflection
    _time += 0.4;
    UpdateReflection();
}
 
/// <summary>
/// Copies an inverted image of the referenced FrameworkElement
/// with a 'ripple' effect
/// </summary>
private void UpdateReflection()
{
    FrameworkElement reflectedFE = ReflectedElement as FrameworkElement;
 
    if (reflectedFE == null)
        return;
 
    // synchronize the element width
    Width = reflectedFE.ActualWidth;
 
    // copy the source into a writeable bitmap
    WriteableBitmap sourceBitmap = new WriteableBitmap(reflectedFE, null);
 
    // create a target which is the same width / height as the reflection element
    WriteableBitmap targetBitmap = new WriteableBitmap((int)ActualWidth, (int)ActualHeight);
 
    // copy the reflection
    for (int y = 0; y < targetBitmap.PixelHeight; y++)
    {
        double amplitude = ComputeAmplitude(y, targetBitmap.PixelHeight);
        double sinusoid = ComputeRipple(y, targetBitmap.PixelHeight, _time);
 
        // the offset to the y value index caused by the ripple
        int yOffset = (int)(sinusoid * amplitude);
 
        // compute the Y position of the line to copy from the source image
        int sourceYLocation = sourceBitmap.PixelHeight - 1 -
            ((y + yOffset) * sourceBitmap.PixelHeight) / targetBitmap.PixelHeight;
 
        // check that this value is in range
        sourceYLocation = Math.Min(sourceBitmap.PixelHeight - 1, Math.Max(0, sourceYLocation));
 
        // copy the required row
        int sourceIndex = sourceYLocation * sourceBitmap.PixelWidth;
        int targetIndex = y * targetBitmap.PixelWidth;
        for (int i = 0; i < targetBitmap.PixelWidth; i++)
        {
            targetBitmap.Pixels[targetIndex++] = sourceBitmap.Pixels[sourceIndex++];
        }                
    }
 
    targetBitmap.Invalidate();
 
    LayoutRoot.Source = targetBitmap;
}
 
/// <summary>
/// Compute the amplitude of the oscillations at a given Y position
/// </summary>
private double ComputeAmplitude(int y, int height)
{
    // our amplitude range is 1 to 3
    return ((double)y * 2) / (double)height + 1.0;
}
 
/// <summary>
/// Compute the sinusoid applied to teh image at the given location
/// </summary>
private double ComputeRipple(int y, int height, double time)
{
    // provide a ripple that is the combination of two out of phase sine waves
    double phaseFactor = (double)y / (double)height;
    return Math.Sin(time + phaseFactor * 16) + Math.Sin(time + phaseFactor * 30)
        + Math.Sin(time + phaseFactor * 62);
}

<UserControl x:Class="SilverlightShimmer.ReflectionControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Width="300" Height="300">
    <Image x:Name="LayoutRoot">
        <Image.OpacityMask>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FF000000" Offset="0"/>
                <GradientStop Color="#00000000" Offset="1"/>
            </LinearGradientBrush>
        </Image.OpacityMask>
    </Image>
</UserControl>

<UserControl x:Class="SilverlightShimmer.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:SilverlightShimmer" Width="320" Height="260">
 
    <Grid Background="Black">
 
        <StackPanel Orientation="Vertical" Margin="10">            
            <Border  x:Name="controlToReflect" BorderThickness="5" BorderBrush="LightGray"
                     CornerRadius="3" HorizontalAlignment="Center">
                <Image  Source="christmas.jpg" Margin="3"
                        Stretch="None"/>
            </Border>
            <local:ReflectionControl x:Name="shimmer" Height="80" Margin="3"
                       ReflectedElement="{Binding ElementName=controlToReflect}"/>
        </StackPanel>
    </Grid>
</UserControl>