System.Drawing.Image img = System.Drawing.Image.FromFile("c:\mm.jpg");
System.IO.MemoryStream ms = new System.IO.MemoryStream();
img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.BinaryWrite(ms.ToArray());
Response.ContentType = "image/jpeg";//指定输出格式为图形