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  1. Tika
  2. TIKA-1678

PDF metadata extraction fails to spot UTF-16 encoded title

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 1.9
    • Fix Version/s: 1.10
    • Component/s: metadata
    • Labels:
      None

      Description

      When extracting metadata from PDFs, we see some odd behaviour for a minority of the documents. The PDF metadata can be encoded as UTF-18 octets, but is not always being decoded as such.

      A specific example is here: http://mqug.org.uk/downloads/201207/201207%20-%20TEC02%20-%20Introduction%20to%20Worklight.pdf

      Which contains this (literal file content):

      443 0 obj
      <</Type/Metadata
      /Subtype/XML/Length 1978>>stream
      <?xpacket begin='' id='W5M0MpCehiHzreSzNTczkc9d'?>
      <?adobe-xap-filters esc="CRLF"?>
      <x:xmpmeta xmlns:x='adobe:ns:meta/' x:xmptk='XMP toolkit 2.9.1-13, framework 1.6'>
      <rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#' xmlns:iX='http://ns.adobe.com/iX/1.0/'>
      <rdf:Description rdf:about='ac9f232e-d341-11e1-0000-ba905bfc4694' xmlns:pdf='http://ns.adobe.com/pdf/1.3/' pdf:Producer='\376\377\000B\000u\000l\000l\000z\000i\000p\000 \000P\000D\000F\000 \000P\000r\000i\000n\000t\000e\000r\000 \000/\000 \000w\000w\000w\000.\000b\000u\000l\000l\000z\000i\000p\000.\000c\000o\000m\000 \000/\000 \000F\000r\000e\000e\000w\000a\000r\000e\000 \000E\000d\000i\000t\000i\000o\000n'/>
      <rdf:Description rdf:about='ac9f232e-d341-11e1-0000-ba905bfc4694' xmlns:xmp='http://ns.adobe.com/xap/1.0/'><xmp:ModifyDate>2012-07-18T15:38:01+01:00</xmp:ModifyDate>
      <xmp:CreateDate>2012-07-18T15:38:01+01:00</xmp:CreateDate>
      <xmp:CreatorTool>UnknownApplication</xmp:CreatorTool></rdf:Description>
      <rdf:Description rdf:about='ac9f232e-d341-11e1-0000-ba905bfc4694' xmlns:xapMM='http://ns.adobe.com/xap/1.0/mm/' xapMM:DocumentID='ac9f232e-d341-11e1-0000-ba905bfc4694'/>
      <rdf:Description rdf:about='ac9f232e-d341-11e1-0000-ba905bfc4694' xmlns:dc='http://purl.org/dc/elements/1.1/' dc:format='application/pdf'><dc:title><rdf:Alt><rdf:li xml:lang='x-default'>\376\377\000M\000i\000c\000r\000o\000s\000o\000f\000t\000 \000P\000o\000w\000e\000r\000P\000o\000i\000n\000t\000 \000-\000 \000I\000n\000t\000r\000o\000d\000u\000c\000t\000i\000o\000n\000 \000t\000o\000 \000W\000o\000r\000k\000l\000i\000g\000h\000t\000 \000\(\000S\000R\000D\000\)\000.\000p\000p\000t\000x</rdf:li></rdf:Alt></dc:title><dc:creator><rdf:Seq><rdf:li>\376\377\000T\000e\000t\000t\000i</rdf:li></rdf:Seq></dc:creator></rdf:Description>
      </rdf:RDF>
      </x:xmpmeta>
      
      
      <?xpacket end='w'?>
      endstream
      endobj
      2 0 obj
      <</Producer(\376\377\000B\000u\000l\000l\000z\000i\000p\000 \000P\000D\000F\000 \000P\000r\000i\000n\000t\000e\000r\000 \000/\000 \000w\000w\000w\000.\000b\000u\000l\000l\000z\000i\000p\000.\000c\000o\000m\000 \000/\000 \000F\000r\000e\000e\000w\000a\000r\000e\000 \000E\000d\000i\000t\000i\000o\000n)
      /CreationDate(D:20120718153801+01'00')
      /ModDate(D:20120718153801+01'00')
      /Title(\376\377\000M\000i\000c\000r\000o\000s\000o\000f\000t\000 \000P\000o\000w\000e\000r\000P\000o\000i\000n\000t\000 \000-\000 \000I\000n\000t\000r\000o\000d\000u\000c\000t\000i\000o\000n\000 \000t\000o\000 \000W\000o\000r\000k\000l\000i\000g\000h\000t\000 \000\(\000S\000R\000D\000\)\000.\000p\000p\000t\000x)
      /Author(\376\377\000T\000e\000t\000t\000i)>>endobj
      

      Presumably, embedding these UTF-16 octet sequences in the XMP RDF is an error, but the ones encoded in the actual PDF metadata fields should be extracted accurately.

      When extracted, we get:

      ...
      dc:title: \376\377\000M\000i\000c\000r\000o\000s\000o\000f\000t\000 \000P\000o\000w\000e\000r\000P\000o\000i\000n\000t\000 \000-\000 \000I\000n\000t\000r\000o\000d\000u\000c\000t\000i\000o\000n\000 \000t\000o\000 \000W\000o\000r\000k\000l\000i\000g\000h\000t\000 \000\(\000S\000R\000D\000\)\000.\000p\000p\000t\000x
      title: \376\377\000M\000i\000c\000r\000o\000s\000o\000f\000t\000 \000P\000o\000w\000e\000r\000P\000o\000i\000n\000t\000 \000-\000 \000I\000n\000t\000r\000o\000d\000u\000c\000t\000i\000o\000n\000 \000t\000o\000 \000W\000o\000r\000k\000l\000i\000g\000h\000t\000 \000\(\000S\000R\000D\000\)\000.\000p\000p\000t\000x
      meta:author: \376\377\000T\000e\000t\000t\000i
      meta:author: Tetti
      ...
      

      So, the author appears to be decoded correctly once, but the title is not. Is the XML dc:title being used to override the PDF title field? Or is one of the title fields being decoded incorrectly?

      (I accept that although this is a real PDF document from the web, it is also a malformed one, so maybe there is not much to be done here.)

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              • Assignee:
                Unassigned
                Reporter:
                anjackson Andrew Jackson
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                • Created:
                  Updated:
                  Resolved: