C# WPF 漂亮的loading 效果

<UserControl x:Class="TestLoadPic.Loading"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300"
             Name="ctl" 
             RenderTransformOrigin="0.5,0.5"
             >
   
    
    <Grid RenderTransformOrigin="0.5,0.5">
        <Ellipse>
            <Ellipse.Fill>
                <RadialGradientBrush>
                    <GradientStop Color="#FFF045AA" Offset="0"/>
                    <GradientStop Color="White" Offset="1"/>
                    <GradientStop Color="#FFFDF1F8" Offset="0.947"/>
                    <GradientStop Color="#FFDA14DA" Offset="0.974"/>
                </RadialGradientBrush>
            </Ellipse.Fill>
        </Ellipse>
        <Ellipse RenderTransformOrigin="0.5,0.5">
            <Ellipse.RenderTransform>
                <TransformGroup>
                    <ScaleTransform x:Name="t" ScaleX="0.0" ScaleY="0.0"/>
                </TransformGroup>
            </Ellipse.RenderTransform>
            <Ellipse.Fill>
                <RadialGradientBrush>
                    <GradientStop Color="#FFF045AA" Offset="0"/>
                    <GradientStop Color="White" Offset="1"/>
             
                </RadialGradientBrush>
            </Ellipse.Fill>

            <Ellipse.Triggers>
                <EventTrigger RoutedEvent ="Loaded">
                    <BeginStoryboard>
                        <Storyboard RepeatBehavior="Forever" AutoReverse="True">
                            <DoubleAnimation  To="1" Storyboard.TargetProperty="ScaleX" Storyboard.TargetName="t" />
                            <DoubleAnimation  To="1" Storyboard.TargetProperty="ScaleY" Storyboard.TargetName="t" />
                        </Storyboard>
                        
                    </BeginStoryboard>
                </EventTrigger>
             </Ellipse.Triggers>
        </Ellipse>

    </Grid>
</UserControl>