how to make image fit to window

<ScrollViewer x:Name="imagescrollviewer" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden">
        <!--<Viewbox>-->
            <Image x:Name="im" Source="{Binding JpgImageSource}" RenderTransformOrigin="0.5,0.5" Stretch="Uniform">
                <Image.RenderTransform>
                    <ScaleTransform  ScaleX="{Binding Value,ElementName=scaleslider}" ScaleY="{Binding Value,ElementName=scaleslider}"/>
                    <!--<RotateTransform Angle="{Binding RotateAngle}"/>-->
                </Image.RenderTransform>
            </Image>
            <!--</Viewbox>-->
        </ScrollViewer>