#region Initialize

        public override void Initialize()
        {
            // define our routine for preparing to show a page.
            // This writes out some tags which we capture in the
            // callback to obtain the page size and orientation.
            this.Execute(string.Format(@"
                /GSNETViewer_PDFpage {{
                    ({0}) print dup == flush
                    pdfgetpage /Page exch store
                    Page /MediaBox pget
                    {{ ({1}) print == flush  }}
                    if
                    Page /CropBox pget
                    {{ ({2}) print == flush }}
                    if
                    Page /Rotate pget not {{ 0 }} if
                    ({3}) print == flush
                }} def", PDF_PAGE_TAG, PDF_MEDIA_TAG, PDF_CROP_TAG, PDF_ROTATE_TAG));

            // put these in userdict so we can write to them later
            this.Execute(@"
                    /Page null def
                    /Page# 0 def
                    /PDFSave null def
                    /DSCPageCount 0 def
                ");

            // open PDF support dictionaries
            this.Execute(@"
                    GS_PDF_ProcSet begin
                    pdfdict begin");
        }

        #endregion

        #region Open

        public override void Open(string filePath)
        {
            // open PDF file
            this.Execute(string.Format("({0}) (r) file pdfopen begin", filePath.Replace("\\", "/")));

            this.Execute("/FirstPage where { pop FirstPage } { 1 } ifelse");
            this.Execute("/LastPage where { pop LastPage } { pdfpagecount } ifelse");

            // flush stdout and then send PDF page marker to stdout where we capture the page numbers via callback
            this.Execute(string.Format("flush ({0}) print exch =only ( ) print =only (\n) print flush", PDF_PAGES_TAG));
        }

        #endregion