使用iTextSharp读取/修改PDF元数据，而不向pdf属性的用户显示任何数据 [英] Read/Modify PDF Metadata using iTextSharp without showing any data to user on pdf properties

问题描述

我正在尝试使用iTextSharp来读取/修改PDF元数据。不向用户显示任何信息。我通过以下代码：

I am trying to use iTextSharp to read/modify PDF metadata. Without showing any information to the user. I gone through below code:

iTextSharp.text.Document document = new iTextSharp.text.Document(iTextSharp.text.PageSize.A4, 20f, 20f, 20f, 20f);
using (MemoryStream memStream = new MemoryStream())
{
    using (PdfWriter wri = PdfWriter.GetInstance(document, memStream))
    {
        document.Open(); document.AddSubject("Test"); document.Close();
    }
}

我非常感谢任何有关解决方案的指示。

I would greatly appreciate any pointers to the solution.

推荐答案

您使用的代码片段是关于向从头创建的PDF文档添加元数据。您要求从现有 PDF文档中读取元数据。请查看iText网站上的文档，更具体地说是Q& A条目如何使用自定义属性从PDF添加/删除/检索信息？

The code snippet you are using is about adding metadata to a PDF document that is created from scratch. You are asking to read metadata from an existing PDF document. Please take a look at the documentation on the iText website, more specifically to Q&A entry How to add / delete / retrieve information from a PDF using a custom property?

当然，使用的代码在这个问题的答案是用Java编写的，但将它移植到C＃相当容易。这是另一个片段：

Granted, the code used in the answer to that question is written in Java, but it's fairly easy to port it to C#. Here's another snippet:

public byte[] ManipulatePdf(byte[] src) {
    PdfReader reader = new PdfReader(src);
    using (MemoryStream ms = new MemoryStream()) {
        using (PdfStamper stamper = new PdfStamper(reader, ms)) {
            Dictionary<String, String> info = reader.Info;
            info["Title"] = "Hello World stamped";
            info["Subject"] = "Hello World with changed metadata";
            info["Keywords"] = "iText in Action, PdfStamper";
            info["Creator"] = "Silly standalone example";
            info["Author"] = "Also Bruno Lowagie";
            stamper.MoreInfo = info;
        }
        return ms.ToArray();
    }
}

您可以通过<从现有PDF检索元数据code> PdfReader 。你得到一个字典，其中的键与ISO-32000-1中信息字典的键对应。如果要更改元数据，可以使用 PdfStamper 进行更改。

You can retrieve the metadata from an existing PDF through PdfReader. You get a Dictionary where the keys correspond with the keys of the info dictionary in ISO-32000-1. If you want to change the metadata, you can do so with PdfStamper.

此功能将读取并调整信息字典（这是您在代码段中引用的内容）。 PDF还可以包含XMP元数据。

This functionality will read and adapt the Info dictionary (which is what you referred to in your code snippet). The PDF can also contains XMP metadata.

XMP元数据可以这样读取：

XMP metadata can be read like this:

public string ReadXmpMetadata(byte[] src) {
    PdfReader reader = new PdfReader(src);
    byte[] b = reader.Metadata;
    return Encoding.UTF8.GetString(b, 0, b.Length);
}  

您可以像这样更改XMP元数据：

You can change the XMP metadata like this:

public byte[] ManipulatePdf(byte[] src) {
    PdfReader reader = new PdfReader(src);
    using (MemoryStream ms = new MemoryStream()) {
        using (PdfStamper stamper = new PdfStamper(reader, ms)) {
            Dictionary<String, String> info = reader.Info;
            using (MemoryStream msXmp = new MemoryStream()) {
                XmpWriter xmp = new XmpWriter(msXmp, info);
                xmp.Close();
                stamper.XmpMetadata = msXmp.ToArray();      
            }
        }
        return ms.ToArray();
    }
}

我假设您知道信息之间的区别字典和PDF格式的XMP元数据流。

I am assuming that you know the difference between the Info dictionary and an XMP metadata stream in PDF.

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