using System;
using System.Drawing;
using System.Windows.Forms;
using com.mxgraph;
using System.Drawing.Imaging;

       void Test1()
       {
           // Creates graph with model
           mxGraph graph = new mxGraph();
           Object parent = graph.GetDefaultParent();

           // Adds cells into the graph
           graph.Model.BeginUpdate();
           try
           {
               Object v1 = graph.InsertVertex(parent, null, "سلام", 20, 20, 80, 30, "strokeColor=#FFCF8A;fillColor=#FFCF8A;gradientColor=white;fontBold=true;fontFamily=tahoma;rounded=true;shadow=true;shape=ellipse");
               Object v2 = graph.InsertVertex(parent, null, "!دنیای ظالم", 200, 150, 80, 30, "rounded=true;shadow=true;fontFamily=tahoma");
               Object e1 = graph.InsertEdge(parent, null, "e1", v1, v2, "fontFamily=tahoma");
           }
           finally
           {
               graph.Model.EndUpdate();
           }

           mxCellRenderer.CreateImage(graph, null, 1,
                                      Color.White, true, null).Save("test.png", ImageFormat.Png);
       }

using System;
using System.Web;
using com.mxgraph;
using System.Drawing;
using System.Web.Services;
using System.IO;
using System.Drawing.Imaging;

namespace test
{
   [WebService(Namespace = "http://tempuri.org/")]
   [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
   public class ImageHandler : IHttpHandler
   {
       public void ProcessRequest(HttpContext context)
       {
           // Creates graph with model
           mxGraph graph = new mxGraph();
           Object parent = graph.GetDefaultParent();

           // Adds cells into the graph
           graph.Model.BeginUpdate();
           try
           {
               Object v1 = graph.InsertVertex(parent, null, "سلام", 20, 20, 80, 30, "strokeColor=#FFCF8A;fillColor=#FFCF8A;gradientColor=white;fontBold=true;fontFamily=tahoma;rounded=true;shadow=true;shape=ellipse");
               Object v2 = graph.InsertVertex(parent, null, "!دنیای ظالم", 200, 150, 80, 30, "rounded=true;shadow=true;fontFamily=tahoma");
               Object e1 = graph.InsertEdge(parent, null, "e1", v1, v2, "fontFamily=tahoma");
           }
           finally
           {
               graph.Model.EndUpdate();
           }

           Image image = mxCellRenderer.CreateImage(graph, null, 1, Color.White, true, null);

           // Render BitMap Stream Back To Client
           MemoryStream memStream = new MemoryStream();
           image.Save(memStream, ImageFormat.Png);

           memStream.WriteTo(context.Response.OutputStream);
       }

       public bool IsReusable
       {
           get
           {
               return false;
           }
       }
   }

}

<img src="ImageHandler.ashx" />