ReportViewer stampare senza background

       public static string StampaReport(ReportViewer v,string pa, int nCopie, string stam)
        {
            try
            {
                SetParameters(v, pa);

                LocalReport report = v.LocalReport;

                byte[] bytes = Render(report, "image");
                tiffs = GetPagine(Image.FromStream(new MemoryStream(bytes)));


                //--- stampo con la classe di .net
                PrintDocument doc = new PrintDocument();
                doc.PrinterSettings.Copies = (short)nCopie;
                doc.PrinterSettings.PrinterName = stam;
                doc.DocumentName = Path.GetFileName(report.ReportPath);
                doc.PrintPage += new PrintPageEventHandler(doc_PrintPage);
                doc.Print();
            }
            catch (Exception ex)
            {
                return ex.ToString();
            }


            return string.Empty;
        }




        static int pag = 0;
        static void doc_PrintPage(object sender, PrintPageEventArgs e)
        {
            e.Graphics.DrawImage(tiffs[pag++], e.PageBounds);
            e.HasMorePages = pag <= tiffs.Count - 1;

            if (!e.HasMorePages)
                pag = 0;
        }

        public static List<Image> GetPagine(Image image)
        {
            List<Image> pagine = new List<Image>();
            FrameDimension dimension = new FrameDimension(image.FrameDimensionsList[0]);

            for (int i = 0; i < image.GetFrameCount(dimension); i++)
            {
                image.SelectActiveFrame(dimension, i);
                pagine.Add(image.Clone() as Image);
            }

            return pagine;
        }