WPF DrawingVisual DrawingContext DrawImage RenderTargetBitmap

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;

namespace WpfApp79
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.Loaded += MainWindow_Loaded;
        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            DrawingVisual visual = new DrawingVisual();
            var drawingContext = visual.RenderOpen();
            drawingContext.DrawImage(new BitmapImage(new Uri(@"../../Images/1.jpg", 
                UriKind.RelativeOrAbsolute)),
                new Rect(0, 0, (int)this.ActualWidth, (int)this.ActualHeight));
            drawingContext.Close();
            var bmp = new RenderTargetBitmap((int)this.ActualWidth,(int)this.ActualHeight,0,0,PixelFormats.Pbgra32);
            bmp.Render(visual);
            this.Background=new ImageBrush(bmp);
        }
    }
}