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);
        }
    }
}

 

 

 

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 WpfApp80
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.WindowState = WindowState.Maximized;
            this.Loaded += MainWindow_Loaded;           
        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            RenderLines(100);
        }

        Random rand = new Random();
        private void RenderLines(int lineCount)
        { 
            int width = (int)this.ActualWidth;
            int height = (int)this.ActualHeight;
            

            // create a visual and a drawing context
            DrawingVisual drawingVisual = new DrawingVisual();
            DrawingContext drawingContext = drawingVisual.RenderOpen();
            
            for (int i = 0; i < lineCount; i++)
            {
                Point startPt=new Point(rand.Next(width), rand.Next(height));
                Point endPt = new Point(rand.Next(width), rand.Next(height));
                var lineColor = Color.FromArgb(
                    a: (byte)rand.Next(255),
                    r: (byte)rand.Next(255),
                    g: (byte)rand.Next(255),
                    b: (byte)rand.Next(255));

                var pen = new Pen(new SolidColorBrush(lineColor), rand.Next(1, 10));

                // draw lines onto the visual's drawing context
                drawingContext.DrawLine(pen, startPt, endPt);
            }
            drawingContext.Close();

            // render the visual on a bitmap
            var bmp = new RenderTargetBitmap((int)this.ActualWidth,(int)this.ActualHeight,0,0,PixelFormats.Pbgra32);
            bmp.Render(drawingVisual);

           this.Background=new ImageBrush(bmp);
        }
    } 
}