WPF Image ZoomIn ZoomOut

//xaml
<Window x:Class="WpfApp109.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:WpfApp109"
        mc:Ignorable="d" WindowState="Maximized"
        Title="{Binding ZoomLevel,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Height="450" Width="800">
    <Grid x:Name="gd" > 
        <Image Source="{Binding ImgUrl,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" MouseWheel="gd_MouseWheel">
            <Image.RenderTransform>
                <ScaleTransform ScaleX="{Binding ZoomLevel,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                                ScaleY="{Binding ZoomLevel,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
                </ScaleTransform>
            </Image.RenderTransform>
        </Image>

    </Grid>
</Window>


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;
using System.ComponentModel;

namespace WpfApp109
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window,INotifyPropertyChanged
    {
        public MainWindow()
        {
            InitializeComponent();
            InitContent();
            this.DataContext= this;
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propName)
        {
            var handler = PropertyChanged;
            if(handler!=null)
            {
                handler?.Invoke(this, new PropertyChangedEventArgs(propName));  
            }
        }

        private string imgUrl;
        public string ImgUrl
        {
            get
            {
                return imgUrl;
            }
            set
            {
                if (value != imgUrl)
                {
                    imgUrl = value;
                    OnPropertyChanged(nameof(ImgUrl));
                }
            }
        }

        private double zoomLevel = 1.0;
        public double ZoomLevel
        {
            get
            {
                return zoomLevel;
            }
            set
            {
                if(value!=zoomLevel) 
                {
                    zoomLevel = value;
                    OnPropertyChanged(nameof(ZoomLevel));
                }
            }
        }
        

        private void InitContent()
        {
            string dir= @"..\..\Images\cl14.jpg";
            string fullDir = System.IO.Path.GetFullPath(dir);
            if(File.Exists(fullDir))
            {
                ImgUrl = fullDir;
            }
        } 

        private void gd_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            if(e.Delta>0)
            {
                ZoomLevel *= 1.2;
            }
            else
            {
                ZoomLevel /= 1.2;
            }
        }
    }
}