How to write a dynamically created bitmap file to response output stream

Thumbnail thumbnail = new Thumbnail(url, 800, 600, width, height);

Bitmap image = thumbnail.GenerateThumbnail();

this.Response.Clear();

this.Response.ClearHeaders();

image.Save(this.Response.OutputStream, ImageFormat.Bmp);

this.Response.ContentType = "image/bmp";

this.Response.AddHeader("content-disposition", "attachment;filename=Thumbnail.bmp");

HttpContext.Current.ApplicationInstance.CompleteRequest();