WPF Image show picture in high resolution periodically via System.Timers.Timer

<Window x:Class="WpfApp411.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:WpfApp411"
        mc:Ignorable="d"
        WindowState="Maximized"
        WindowStyle="None"
        KeyDown="Window_KeyDown"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Image Source="{Binding ImgUrl,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
               RenderOptions.BitmapScalingMode="Fant"
               />
        <TextBlock Text="{Binding Num,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                   Foreground="Red"
                   FontSize="50"
                   HorizontalAlignment="Right"
                   VerticalAlignment="Bottom"
                   Width="200"
                   Panel.ZIndex="2"/>
    </Grid>
</Window>



//cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
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.Diagnostics.Eventing.Reader;

namespace WpfApp411
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged
    {

        public MainWindow()
        {
            InitializeComponent();
            imgsList = new List<string>(Directory.GetFiles(@"../../Images"));
            imgsCount = imgsList.Count;
            if (imgsCount > 0)
            {
                ImgUrl = imgsList[imgIdx];
                System.Timers.Timer tmr = new System.Timers.Timer();
                tmr.Elapsed += Tmr_Elapsed;
                tmr.Interval = 10;
                tmr.Start();
                this.DataContext = this;
            }
        }

        private void Tmr_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            if(isPaused)
            {
                return;
            }

            if (++imgIdx >= imgsCount)
            {
                imgIdx = 0;
            }
            ImgUrl = imgsList[imgIdx];
            ++Num;
        }

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

        private List<string> imgsList { get; set; }
        private int imgsCount = 0;
        private bool isPaused = false;

        private int imgIdx = 0;

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

        private int num = 0;
        public int Num
        {
            get
            {
                return num;
            }
            set
            {
                if (value != num)
                {
                    num = value;
                    OnPropertyChanged(nameof(Num));
                }
            }
        }

        private void Window_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Space)
            {
                isPaused = !isPaused;
            }
            else if (Keyboard.Modifiers == ModifierKeys.Control && e.Key == Key.C)
            {
                var msgResult = MessageBox.Show("Are you sure to exit this window?", "Exit", MessageBoxButton.YesNo,
                    MessageBoxImage.Question, MessageBoxResult.Yes);
                if (msgResult == MessageBoxResult.Yes)
                {
                    this.Close();
                }
            }
        }
    }
}