如何从pdf文件中提取所有链接？

Question

按照标准，链接隐藏在注释中（规范第12.5.6.5节）。从那里提取地址很容易：Extracting links to pages in another PDF from PDF using Python or other method 但链接通常不是像文档中的特殊对象那样显示的，而是像“http://blah-blah.com”这样的纯文本。如何不仅从注释中提取链接，而且从文本本身提取链接？我可以搜索整个文本并找到像“http://”这样的单词，但是有没有更好的解决方案？PDF编辑器也在突出显示文本链接，他们怎么知道这段文本是超链接？

Answer 1

遗憾的是，url不是作为注释保存的，而是简单地嵌入到内容文本中，在pdf中没有特殊的可见性。除了搜索PDF的完整文本和匹配url的模式之外，没有其他解决方案。

Answer 2

字符串“somePDFfile.pdf”| grep http

Answer 3

我刚刚制作了pdfx，这是一个用于此工作的小工具：从给定的PDF下载所有PDF。它是用Python编写的，并在GPLv3许可下作为open source发布的：http://www.metachris.com/pdfx

您可以使用pdfx工具显示所有PDF url、所有url（使用-v）以及下载所有引用的PDF（使用-d）：

$ pdfx https://weakdh.org/imperfect-forward-secrecy.pdf -d ./
Reading url 'https://weakdh.org/imperfect-forward-secrecy.pdf'...
Saved pdf as './imperfect-forward-secrecy.pdf'
Document infos:
- CreationDate = D:20150821110623-04'00'
- Creator = LaTeX with hyperref package
- ModDate = D:20150821110805-04'00'
- PTEX.Fullbanner = This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian) kpathsea version 6.1.1
- Producer = pdfTeX-1.40.14
- Title = Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice
- Trapped = False
- Pages = 13

Analyzing text...
- URLs: 49
- URLs to PDFs: 17

JSON summary saved as './imperfect-forward-secrecy.pdf.infos.json'

Downloading 17 referenced pdfs...
Created directory './imperfect-forward-secrecy.pdf-referenced-pdfs'
Downloaded 'http://cr.yp.to/factorization/smoothparts-20040510.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/smoothparts-20040510.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35517.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35517.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35514.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35514.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35519.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35519.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35522.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35522.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35509.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35509.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35528.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35528.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35513.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35513.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35533.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35533.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35551.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35551.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35527.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35527.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35520.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35520.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35526.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35526.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35515.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35515.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35529.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35529.pdf'...
Downloaded 'http://cryptome.org/2013/08/spy-budget-fy13.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/spy-budget-fy13.pdf'...
Downloaded 'http://www.spiegel.de/media/media-35671.pdf' to './imperfect-forward-secrecy.pdf-referenced-pdfs/media-35671.pdf'...

您可以使用$ easy_install -U pdfx安装它。

在引擎盖下，pdfx使用PyPDF2，一个Python库读取PDF内容，然后使用regular expression to match all urls。