我有以下问题。我有一个PDF文件，其中包含一个XML文件作为注释。不是嵌入文件而是注释。现在我尝试使用以下链接中的代码阅读它：
iTextSharp - how to open/read/extract a file attachment?
它适用于嵌入式文件，但不适用于作为注释的文件附件。
我谷歌从PDF中提取注释，并找到以下链接：Reading PDF Annotations with iText
所以注释类型是“文件附件注释”
有人能展示一个有效的例子吗？
在此先感谢您的帮助
在有关iText和iTextSharp的问题中，人们应该首先看看keyword list on itextpdf.com。在这里，您可以找到File attachment, extract attachments引用来自iText in Action — 2nd Edition的两个Java样本：
旧关键字列表已不复存在; itextpdf.com网站现在提供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，我再次有死链接...
基于iText in Action — Second Edition的相关iText示例如下：
（我没有找到.Net和iText 7的样本端口，但根据其他来源，这个端口不应该太难......）
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来提取文档级附件：
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在一些ZIP文件中，而Java版本将它们放入文件系统......哦......）