Image is not getting printed when print button is clicked?

public static void PrintWebControl(Control ctrl)
{
    PrintWebControl(ctrl, string.Empty);
}

public static void PrintWebControl(Control ctrl, string Script)
{
    StringWriter stringWrite = new StringWriter();
    System.Web.UI.HtmlTextWriter htmlWrite = new System.Web.UI.HtmlTextWriter(stringWrite);
    if (ctrl is WebControl)
    {
        Unit w = new Unit(100, UnitType.Percentage); ((WebControl)ctrl).Width = w;
    }
    Page pg = new Page();
    pg.EnableEventValidation = false;
    if (Script != string.Empty)
    {
        pg.ClientScript.RegisterStartupScript(pg.GetType(),"PrintJavaScript", Script);
    }
    HtmlForm frm = new HtmlForm();
    pg.Controls.Add(frm);
    frm.Attributes.Add("runat", "server");
    frm.Controls.Add(ctrl);
    pg.DesignerInitialize();
    pg.RenderControl(htmlWrite);
    string strHTML = stringWrite.ToString();


    PaperSize p = null;
    PrintDocument pd = new PrintDocument();


    pd.PrinterSettings.DefaultPageSettings.Landscape = true;
    pd.DefaultPageSettings.PaperSize = p;

    HttpContext.Current.Response.Clear();
    HttpContext.Current.Response.Write(@"<link href='/Style1.css' rel='stylesheet' type='text/css' />");
    HttpContext.Current.Response.Write(strHTML);
    HttpContext.Current.Response.Write("<script>window.print();</script>");
    HttpContext.Current.Response.End();
}
protected void Print_Button_Click(object sender, EventArgs e)
{
    PrintInvoice.PrintWebControl(Panel1);
}