iTextSharp.text.pdf.BaseFont.CreateSubsetPrefix C# (CSharp) Метод

        public static string CreateSubsetPrefix()
        {
            char[] s = new char[7];
            lock (random) {
                for (int k = 0; k < 6; ++k)
                    s[k] = (char)(random.Next('A', 'Z' + 1));
            }
            s[6] = '+';
            return new String(s);
        }

        /**
         * @see TtfUnicodeWriter#writeFont(TrueTypeFontUnicode, PdfIndirectReference, Object[], byte[])
         */
        internal protected override void WriteFont(TrueTypeFontUnicode font, PdfIndirectReference refer, Object[] parameters, byte[] rotbits)
        {
            Dictionary <int, int[]> longTag = (Dictionary <int, int[]>)parameters[0];

            font.AddRangeUni(longTag, true, font.Subset);
            int [][] metrics = new int[longTag.Count][];
            longTag.Values.CopyTo(metrics, 0);
            Array.Sort(metrics, font);
            PdfIndirectReference ind_font = null;
            PdfObject            pobj     = null;
            PdfIndirectObject    obj      = null;

            if (font.Cff)
            {
                byte[] b = font.ReadCffFont();
                if (font.Subset || font.SubsetRanges != null)
                {
                    CFFFontSubset cff = new CFFFontSubset(new RandomAccessFileOrArray(b), longTag);
                    try
                    {
                        b = cff.Process(cff.GetNames()[0]);
                    }
                    catch (Exception e)
                    {
                        //temporary fix for cff subset failure
                        font.Subset = false;
                        font.AddRangeUni(longTag, true, font.Subset);
                        metrics = new int[longTag.Count][];
                        longTag.Values.CopyTo(metrics, 0);
                        Array.Sort(metrics, font);
                    }
                }
                pobj     = new BaseFont.StreamFont(b, "CIDFontType0C", font.CompressionLevel);
                obj      = writer.AddToBody(pobj);
                ind_font = obj.IndirectReference;
            }
            else
            {
                byte[] b;
                if (font.Subset || font.DirectoryOffset != 0)
                {
                    lock (font.Rf) {
                        TrueTypeFontSubSet sb = new TrueTypeFontSubSet(font.FileName, new RandomAccessFileOrArray(font.Rf), new HashSet2 <int>(longTag.Keys), font.DirectoryOffset, false, false);
                        b = sb.Process();
                    }
                }
                else
                {
                    b = font.GetFullFont();
                }
                int[] lengths = new int[] { b.Length };
                pobj     = new BaseFont.StreamFont(b, lengths, font.CompressionLevel);
                obj      = writer.AddToBody(pobj);
                ind_font = obj.IndirectReference;
            }
            // CIDSet shall be based on font.maxGlyphId property of the font, it is maxp.numGlyphs for ttf,
            // because technically we convert all unused glyphs to space, e.g. just remove outlines.
            byte[] cidSetBytes = new byte[font.MaxGlyphId / 8 + 1];
            for (int i = 0; i < font.MaxGlyphId / 8; i++)
            {
                cidSetBytes[i] |= 0xff;
            }
            for (int i = 0; i < font.MaxGlyphId % 8; i++)
            {
                cidSetBytes[cidSetBytes.Length - 1] |= rotbits[i];
            }
            PdfStream stream = new PdfStream(cidSetBytes);

            stream.FlateCompress(font.CompressionLevel);
            PdfIndirectReference cidset = writer.AddToBody(stream).IndirectReference;

            String subsetPrefix = "";

            if (font.Subset)
            {
                subsetPrefix = BaseFont.CreateSubsetPrefix();
            }
            PdfDictionary dic = font.GetFontDescriptor(ind_font, subsetPrefix, cidset);

            obj      = writer.AddToBody(dic);
            ind_font = obj.IndirectReference;

            pobj     = font.GetCIDFontType2(ind_font, subsetPrefix, metrics);
            obj      = writer.AddToBody(pobj);
            ind_font = obj.IndirectReference;

            pobj = font.GetToUnicode(metrics);
            PdfIndirectReference toUnicodeRef = null;

            if (pobj != null)
            {
                obj          = writer.AddToBody(pobj);
                toUnicodeRef = obj.IndirectReference;
            }

            pobj = font.GetFontBaseType(ind_font, subsetPrefix, toUnicodeRef);
            writer.AddToBody(pobj, refer);
        }