c# - 使用 iTextSharp 读取 PDF 文件附件注释

Question

我有以下问题。我有一个 PDF，其中附有作为注释的 XML 文件。 不是作为嵌入文件，而是作为注释。现在我尝试使用以下链接中的代码来阅读它:

iTextSharp - how to open/read/extract a file attachment?

它适用于嵌入文件，但不适用于作为注释的文件附件。

我在 Google 上搜索从 PDF 中提取注释并找到以下链接: Reading PDF Annotations with iText

因此注释类型为“文件附件注释”

有人可以展示一个可行的示例吗？

预先感谢您的帮助

Answer 1

正如在有关 iText 和 iTextSharp 的问题中经常出现的那样，我们应该首先查看 keyword list on itextpdf.com 。在这里你可以找到File attachment, extract attachments引用 iText in Action — 2nd Edition 中的两个 Java 示例:

旧的关键字列表不再存在； itextpdf.com 网站现在提供了其他搜索示例的方法，但我不会描述它们，以免网站再次更改并且我再次出现死链接...

基于iText in Action — Second Edition的相关iText示例是:

• 第4部分.第16章.KubrickDvds

• Java, iText 5.x
• Java, iText 7.x
• .Net, iText 5.x

• 第4部分.第16章.库布里克纪录片

• Java, iText 5.x
• Java, iText 7.x
• .Net, iText 5.x

这里是Samples from iText5

(我还没有找到示例到 .Net 和 iText 7 的端口，但根据其他来源，这个端口应该不会太困难...)

KubrickDvds 包含以下方法 extractAttachments/ExtractAttachments 来提取文件附件注释:

Java、iText 5.x:

/**
 * Extracts attachments from an existing PDF.
 * @param src   the path to the existing PDF
 */
public void extractAttachments(String src) throws IOException {
    PdfReader reader = new PdfReader(src);
    PdfArray array;
    PdfDictionary annot;
    PdfDictionary fs;
    PdfDictionary refs;
    for (int i = 1; i <= reader.getNumberOfPages(); i++) {
        array = reader.getPageN(i).getAsArray(PdfName.ANNOTS);
        if (array == null) continue;
        for (int j = 0; j < array.size(); j++) {
            annot = array.getAsDict(j);
            if (PdfName.FILEATTACHMENT.equals(annot.getAsName(PdfName.SUBTYPE))) {
                fs = annot.getAsDict(PdfName.FS);
                refs = fs.getAsDict(PdfName.EF);
                for (PdfName name : refs.getKeys()) {
                    FileOutputStream fos
                        = new FileOutputStream(String.format(PATH, fs.getAsString(name).toString()));
                    fos.write(PdfReader.getStreamBytes((PRStream)refs.getAsStream(name)));
                    fos.flush();
                    fos.close();
                }
            }
        }
    }
    reader.close();
}

Java、iText 7.x:

public void extractAttachments(String src) throws IOException {
    PdfDocument pdfDoc = new PdfDocument(new PdfReader(src));
    PdfReader reader = new PdfReader(src);
    PdfArray array;
    PdfDictionary annot;
    PdfDictionary fs;
    PdfDictionary refs;
    for (int i = 1; i <= pdfDoc.getNumberOfPages(); i++) {
        array = pdfDoc.getPage(i).getPdfObject().getAsArray(PdfName.Annots);
        if (array == null) continue;
        for (int j = 0; j < array.size(); j++) {
            annot = array.getAsDictionary(j);
            if (PdfName.FileAttachment.equals(annot.getAsName(PdfName.Subtype))) {
                fs = annot.getAsDictionary(PdfName.FS);
                refs = fs.getAsDictionary(PdfName.EF);
                for (PdfName name : refs.keySet()) {
                    FileOutputStream fos
                            = new FileOutputStream(String.format(PATH, fs.getAsString(name).toString()));
                    fos.write(refs.getAsStream(name).getBytes());
                    fos.flush();
                    fos.close();
                }
            }
        }
    }
    reader.close();
}

C#、iText 5.x:

/**
 * Extracts attachments from an existing PDF.
 * @param src the path to the existing PDF
 * @param zip the ZipFile object to add the extracted images
 */
public void ExtractAttachments(byte[] src, ZipFile zip) {
  PdfReader reader = new PdfReader(src);
  for (int i = 1; i <= reader.NumberOfPages; i++) {
    PdfArray array = reader.GetPageN(i).GetAsArray(PdfName.ANNOTS);
    if (array == null) continue;
    for (int j = 0; j < array.Size; j++) {
      PdfDictionary annot = array.GetAsDict(j);
      if (PdfName.FILEATTACHMENT.Equals(
          annot.GetAsName(PdfName.SUBTYPE)))
      {
        PdfDictionary fs = annot.GetAsDict(PdfName.FS);
        PdfDictionary refs = fs.GetAsDict(PdfName.EF);
        foreach (PdfName name in refs.Keys) {
          zip.AddEntry(
            fs.GetAsString(name).ToString(), 
            PdfReader.GetStreamBytes((PRStream)refs.GetAsStream(name))
          );
        }
      }
    }
  }
}

KubrickDocumentary 包含以下方法 extractDocLevelAttachments/ExtractDocLevelAttachments 用于提取文档级附件:

Java、iText 5.x:

/**
 * Extracts document level attachments
 * @param filename     a file from which document level attachments will be extracted
 * @throws IOException
 */
public void extractDocLevelAttachments(String filename) throws IOException {
    PdfReader reader = new PdfReader(filename);
    PdfDictionary root = reader.getCatalog();
    PdfDictionary documentnames = root.getAsDict(PdfName.NAMES);
    PdfDictionary embeddedfiles = documentnames.getAsDict(PdfName.EMBEDDEDFILES);
    PdfArray filespecs = embeddedfiles.getAsArray(PdfName.NAMES);
    PdfDictionary filespec;
    PdfDictionary refs;
    FileOutputStream fos;
    PRStream stream;
    for (int i = 0; i < filespecs.size(); ) {
      filespecs.getAsString(i++);
      filespec = filespecs.getAsDict(i++);
      refs = filespec.getAsDict(PdfName.EF);
      for (PdfName key : refs.getKeys()) {
        fos = new FileOutputStream(String.format(PATH, filespec.getAsString(key).toString()));
        stream = (PRStream) PdfReader.getPdfObject(refs.getAsIndirectObject(key));
        fos.write(PdfReader.getStreamBytes(stream));
        fos.flush();
        fos.close();
      }
    }
    reader.close();
}

Java、iText 7.x

public void extractDocLevelAttachments(String src) throws IOException {
    PdfDocument pdfDoc = new PdfDocument(new PdfReader(src));
    PdfDictionary root = pdfDoc.getCatalog().getPdfObject();
    PdfDictionary documentnames = root.getAsDictionary(PdfName.Names);
    PdfDictionary embeddedfiles = documentnames.getAsDictionary(PdfName.EmbeddedFiles);
    PdfArray filespecs = embeddedfiles.getAsArray(PdfName.Names);
    PdfDictionary filespec;
    PdfDictionary refs;
    FileOutputStream fos;
    PdfStream stream;
    for (int i = 0; i < filespecs.size(); ) {
        filespecs.getAsString(i++);
        filespec = filespecs.getAsDictionary(i++);
        refs = filespec.getAsDictionary(PdfName.EF);
        for (PdfName key : refs.keySet()) {
            fos = new FileOutputStream(String.format(PATH, filespec.getAsString(key).toString()));
            stream = refs.getAsStream(key);
            fos.write(stream.getBytes());
            fos.flush();
            fos.close();
        }
    }
    pdfDoc.close();
}

C#、iText 5.x:

/**
 * Extracts document level attachments
 * @param PDF from which document level attachments will be extracted
 * @param zip the ZipFile object to add the extracted images
 */
public void ExtractDocLevelAttachments(byte[] pdf, ZipFile zip) {
  PdfReader reader = new PdfReader(pdf);
  PdfDictionary root = reader.Catalog;
  PdfDictionary documentnames = root.GetAsDict(PdfName.NAMES);
  PdfDictionary embeddedfiles = 
      documentnames.GetAsDict(PdfName.EMBEDDEDFILES);
  PdfArray filespecs = embeddedfiles.GetAsArray(PdfName.NAMES);
  for (int i = 0; i < filespecs.Size; ) {
    filespecs.GetAsString(i++);
    PdfDictionary filespec = filespecs.GetAsDict(i++);
    PdfDictionary refs = filespec.GetAsDict(PdfName.EF);
    foreach (PdfName key in refs.Keys) {
      PRStream stream = (PRStream) PdfReader.GetPdfObject(
        refs.GetAsIndirectObject(key)
      );
      zip.AddEntry(
        filespec.GetAsString(key).ToString(), 
        PdfReader.GetStreamBytes(stream)
      );
    }
  }
}

(出于某种原因，C# 示例将提取的文件放入某个 ZIP 文件中，而 Java 版本将它们放入文件系统中...哦好吧...)