如何在Viewbox中显示大小相同的图像？

I have the following code:

我有以下代码：

<StackPanel Orientation="Vertical">
    <Viewbox Height="100" >

        <Canvas x:Name="pluginTile" Style="{StaticResource productImageTopFade}" Width="320" Height="200">
            <Image Panel.ZIndex="1" Source="{Binding PluginImagePath}" Margin="0,10,15,0"  ></Image>
            <Canvas.Effect>
                <DropShadowEffect ShadowDepth="2" Opacity="0.15" Direction="270" BlurRadius="20" />
            </Canvas.Effect>
         </Canvas>
    </Viewbox>
    <Border BorderBrush="Transparent" BorderThickness="1">
        <Label FontWeight="Normal" Name="ProductName"  Content="{Binding NameAndEdition}" Margin="0 0 0 0" VerticalAlignment="Bottom" HorizontalAlignment="Center" Foreground="Gray"   />
    </Border></StackPanel>
<StackPa