iText7 For .Net 系列文章（三）文本注释、注释回复、链接注释

　　在文档中增加注释或者评论，这是非常常用，PDF文档也包含这样的功能，在现有PDF文档上增加文本注释、对之前的注释进行回复。在Word、Excel还有链接的功能，跳转到本Word中其他位置（类似导航栏）、其他Word中莫个位置、甚至某个网址还有其他的功能，PDF也支持这些操作，这是只是以简单的超链接为例，可根据具体情况创建不同的PDFAction来执行不同的链接注释点击行为。不多说，直接上代码，可以对着练练手，然后工作中具体用到某个功能时再去具体仔细分析需要怎么改。

        #region Chapter 4
        private void textAnnotationToolStripMenuItem_Click(object sender, EventArgs e)
        {
            var fullFileName = GetSavingFileNameContainDirectory();
            if (string.IsNullOrWhiteSpace(fullFileName)) return;
            using (var fos = new FileStream(fullFileName, FileMode.Create))
            {
                //Initialize PDF document
                PdfDocument pdf = new PdfDocument(new PdfWriter(fos));
                // Initialize document
                Document document = new Document(pdf);
                PdfFont yaHeiFont = PdfFontFactory.CreateRegisteredFont("yaHei_font", PdfEncodings.IDENTITY_H, EmbeddingStrategy.FORCE_EMBEDDED);
                Paragraph p = new Paragraph().SetFont(yaHeiFont).SetFontSize(12).Add("这是一段含有注解的文本。");
                document.Add(p);
                var pdfPage = pdf.GetFirstPage();
                //Create text annotation
                PdfAnnotation ann = new PdfTextAnnotation(new Rectangle(20, 800, 0, 0))
                    .SetOpen(true)
                    .SetColor(new DeviceRgb(System.Drawing.Color.Green.R, System.Drawing.Color.Green.G, System.Drawing.Color.Green.B))
                    .SetTitle(new PdfString("iText"))
                    .SetContents("With iText, you can truly take your documentation needs to the next level.");
                //ann.SetFlag(iText.Kernel.Pdf.Annot.PdfAnnotation.INVISIBLE);
                pdfPage.AddAnnotation(ann);

                document.Close();

            }
        }

        private void replyAnnotaionToolStripMenuItem_Click(object sender, EventArgs e)
        {
            var src = GetOpeningFileNameContainDirectory("PDF(*.pdf)|*.pdf");
            var dest = GetSavingFileNameContainDirectory();
            if (string.IsNullOrWhiteSpace(src) || string.IsNullOrWhiteSpace(dest)) return;
            PdfDocument pdfDoc = new PdfDocument(new PdfReader(src), new PdfWriter(dest));
            PdfPage firstPage = pdfDoc.GetFirstPage();
            IList<PdfAnnotation> annots = firstPage.GetAnnotations();

            Rectangle stickyRectangle = annots[0].GetRectangle().ToRectangle();
            PdfAnnotation replySticky = new PdfTextAnnotation(stickyRectangle)
                // This method specifies whether the annotation will initially be displayed open.
                .SetOpen(true)
                .SetIconName(new PdfName("Comment"))

                // This method sets an annotation to which the current annotation is "in reply".
                // Both annotations shall be on the same page of the document.
                .SetInReplyTo(annots[0])

                // This method sets the text label that will be displayed in the title bar of the annotation's pop-up window
                // when open and active. This entry shall identify the user who added the annotation.
                .SetText(new PdfString("Reply"))

                // This method sets the text that will be displayed for the annotation or the alternate description,
                // if this type of annotation does not display text.
                .SetContents("Hello PDF")
                .SetColor(new DeviceRgb(System.Drawing.Color.Green.R, System.Drawing.Color.Green.G, System.Drawing.Color.Green.B));

            firstPage.AddAnnotation(replySticky);

            pdfDoc.Close();
        }

        private void linkAnnotationToolStripMenuItem_Click(object sender, EventArgs e)
        {
            var dest = GetSavingFileNameContainDirectory();
            if (string.IsNullOrWhiteSpace(dest)) return;
            PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
            Document document = new Document(pdfDoc);
            // Create link annotation
            PdfLinkAnnotation annotation = (new PdfLinkAnnotation(new Rectangle(0, 0)).SetAction(PdfAction.CreateURI("https://itextpdf.com/")));

            Link link = new Link("here", annotation);
            Paragraph p = new Paragraph("The example of link annotation. Click ").Add(link.SetUnderline()).Add(" to learn more...");

            document.Add(p);
            document.Close();
        }

        #endregion

        private string GetSavingFileNameContainDirectory(string filter = "PDF(*.pdf)|*.pdf")
        {
            saveFileDialog1.Filter = filter;
            saveFileDialog1.AddExtension = true;
            saveFileDialog1.ShowDialog();
            return saveFileDialog1.FileName;
        }

        private string GetOpeningFileNameContainDirectory(string fileter = "CSV(*.CSV)|*.csv|txt files(*.txt)|*.txt")
        {
            openFileDialog1.Filter = fileter;
            openFileDialog1.ShowDialog();
            return openFileDialog1.FileName;
        }

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