WPF Image zoomin zoomout move

//xaml
<Window x:Class="WpfApp145.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp145"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="200"/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <ListBox Grid.Column="0" x:Name="lbx" SelectedIndex="0" SelectionChanged="lbx_SelectionChanged" >
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <Image Source="{Binding Content,RelativeSource={RelativeSource AncestorType=ListBoxItem}}" 
                           Width="200" Height="500"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
        <Image Grid.Column="1" x:Name="img"  Source="{Binding SelectedItem,ElementName=lbx}" 
                   ClipToBounds="True"
                  MouseDown="img_MouseDown" MouseMove="img_MouseMove" MouseUp="img_MouseUp"
                 MouseWheel="img_MouseWheel">
            <Image.RenderTransform>
                <TransformGroup>
                    <ScaleTransform x:Name="scaler"/>
                    <TranslateTransform x:Name="translater"/>
                </TransformGroup>
            </Image.RenderTransform>
        </Image>
    </Grid>
</Window>


//cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;

namespace WpfApp145
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            InitLbx();
        }

        private void InitLbx()
        {
            var files = Directory.GetFiles(@"..\..\Images", "*", SearchOption.AllDirectories);
            lbx.ItemsSource = files;
        }

        Point prePoint { get; set; }
        bool isMoving { get; set; }
        private void img_MouseDown(object sender, MouseButtonEventArgs e)
        {
            prePoint = e.GetPosition(img);
        }

        private void img_MouseMove(object sender, MouseEventArgs e)
        {
            isMoving = true;
        }

        private void img_MouseUp(object sender, MouseButtonEventArgs e)
        {
            if (isMoving && e.ChangedButton == MouseButton.Left && e.ButtonState == MouseButtonState.Released)
            {
                Point newPoint = e.GetPosition(img);
                translater.X += newPoint.X - prePoint.X;
                translater.Y += newPoint.Y - prePoint.Y;
                isMoving = false;
            }
        }

        private void img_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            if (e.Delta > 0)
            {
                scaler.ScaleX *= 1.2;
                scaler.ScaleY *= 1.2;
            }
            else
            {
                scaler.ScaleX /= 1.2;
                scaler.ScaleY /= 1.2;
            }
            scaler.CenterX = e.GetPosition(img).X;
            scaler.CenterY = e.GetPosition(img).Y;
        }

        private void lbx_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            scaler.ScaleX = 1.0;
            scaler.ScaleY = 1.0;
            translater.X = 0;
            translater.Y = 0;
        }
    }
}