gistfile1.cs

using System;
using System.IO;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace WebApplication3
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Canvas canvas = new Canvas
                                {
                                    Width = 200,
                                    Height = 200,
                                    Background = Brushes.LightGray
                                };

            canvas.Children.Add(new Label { Content = "初春かわいい" });
            canvas.Arrange(new Rect(0, 0, canvas.Width, canvas.Height));

            RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap((Int32)canvas.Width, (Int32)canvas.Height, 96, 96, PixelFormats.Default);
            renderTargetBitmap.Render(canvas);

            MemoryStream memoryStream = new MemoryStream();
            BitmapEncoder encoder = new PngBitmapEncoder();
            encoder.Frames.Add(BitmapFrame.Create(renderTargetBitmap));
            encoder.Save(memoryStream);

            Response.ContentType = "image/png";
            Response.ClearContent();
            Response.BinaryWrite(memoryStream.ToArray());
        }
    }
}