WPF中Button的背景图片，实现禁止IsMouseOver时显示默认

<Button x:Name="btnPickUpNum" Click="PickUpNum_OnClick" Grid.Row="1" Grid.Column="2">
<Button.Template>
<ControlTemplate TargetType="Button">
<ContentControl Name="cc">
<Image Source="/Images/pickupnum.jpg"></Image>
</ContentControl>
</ControlTemplate>
</Button.Template>
</Button>