RenderTargetBitmap把visual转换为图像

using System;
            using System.Windows;
            using System.Windows.Controls;
            using System.Windows.Media;
            using System.Windows.Media.Imaging;
            using System.Globalization;
            namespace SDKSample
            {
            public partial class RenderTargetBitmapExample : Page
            {
            public RenderTargetBitmapExample()
            {
            Image myImage = new Image();
            FormattedText text = new FormattedText("ABC",
            new CultureInfo("en-us"),
            FlowDirection.LeftToRight,
            new Typeface(this.FontFamily, FontStyles.Normal, FontWeights.Normal, new FontStretch()),
            this.FontSize,
            this.Foreground);
            DrawingVisual drawingVisual = new DrawingVisual();
            DrawingContext drawingContext = drawingVisual.RenderOpen();
            drawingContext.DrawText(text, new Point(2, 2));
            drawingContext.Close();
            RenderTargetBitmap bmp = new RenderTargetBitmap(180, 180, 120, 96, PixelFormats.Pbgra32);
            bmp.Render(drawingVisual);
            myImage.Source = bmp;
            // Add Image to the UI
            StackPanel myStackPanel = new StackPanel();
            myStackPanel.Children.Add(myImage);
            this.Content = myStackPanel;
            }
            }
            }