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What are the permitted compression techniques for PDF/A-1?

May 27, 2012 7:27 PM

Tags: #compression #pdf/a #pdf/a-1b #pdf/a1a

The PDF/A-1 standard does not specify how compression is performed. What are the permitted compression techniques for PDF/A-1?

 

The information I have gathered (not sure if all are true)

 

  1. LZW should not be used
  2. JPEG2000 may not be used
  3. Few say, JPEG can be used but its a lossy compression. (PDF standard clearly states lossy compression can't be used)

 

 

Also, how to figure out whether a particular file is PDF/A-1a or PDF/A-1b and what kind of compressions are used in that file?

 

 

Thanks in advance.

 
Replies
  • Currently Being Moderated
    May 27, 2012 8:25 PM   in reply to hariharan1986

    Adobe Acrobat Pro provides preflight profiles for testing whether a PDF file conforms to any of PDF/A or PDF/X standards. There are also options for converting a non-compliant PDF file to any one of those standards if such fixups are possible.

     

    FYI, there are specifications for the different PDF/A and PDF/X specifications that you may purchase (either hardcopy or downloadable PDF files) from ISO.

     

              - Dov

     
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  • Currently Being Moderated
    May 27, 2012 8:37 PM   in reply to hariharan1986

    Another trick in Acrobat Pro is to invoke the Output Preview tool (under “print production”) and choose the Object Inspector instead of the Separations function. Then click on a particular image. You will see what type of compression is used, the image resolution, the color space (including ICC profile if appropriate), etc. That same tool also shows what font a text is formatted in and point size as well as attributes of other PDF objects as well. It is exceptionally useful in determining what you have in a PDF file.

     

    If you want to look at everything at once, under Preflight, pull down Options and invoke Create Inventory. That function will create a monstrous PDF detailing all the objects and features of the PDF file in question!

     

              - Dov

     
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  • Currently Being Moderated
    May 27, 2012 9:49 PM   in reply to hariharan1986

    For better or worse, ISO specifications are written in a language from a parallel universe.    After dealing with ISO standards for a while, you learn what specific words really mean. I should know - I am chair of the ISO PDF/X task force and co-chair of the PDF/VT task force.

     

    The word should does not specify a requirement. PDF/A does not prohibit lossy compression.

     

    JPEG is always a lossy compression. There is a mode of JPEG2000 compression that is indeed lossless. Note that JPEG and JPEG2000 are totally different compression schemes. (I believe that PDF/A-1 as well as PDF/X-1a and PDF/X-3, based on older versions of the PDF specification do not permit JPEG2000. PDF/A-2 based on ISO32000-1 and PDF/X-4 based on PDF 1.6 do allow for JPEG2000.)

     

    ZIP compression is lossless.

     

              - Dov

     
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  • Currently Being Moderated
    May 27, 2012 11:35 PM   in reply to hariharan1986

    Run the preflight in Acrobat. It provides exact information as to what failed.

     

              - Dov

     
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  • Currently Being Moderated
    May 28, 2012 7:06 PM   in reply to hariharan1986

    As PDF/A-2 has only been a standard for about 6 months now, I am not aware of any scanners that are producing PDF/A-2.  However, the only advantage of PDF/A-2 for scanning – which is important – is support for JPEG2000.

     
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    May 28, 2012 10:33 PM   in reply to hariharan1986

    Not aware of any such MFPs or even standalone scanners that produce PDF/A-2 yet.

     

              - Dov

     
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  • Currently Being Moderated
    Jun 6, 2012 11:26 PM   in reply to hariharan1986

    Based on the fact that anomalies are fixed as we release newer releases, I would assume that the results you get in Acrobat 10 are the correct ones.

     

              - Dov

     
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  • Currently Being Moderated
    Jun 14, 2012 6:35 AM   in reply to hariharan1986

    What is being used to create the PDF file, Acrobat itself or a scanner or an MFP?

     

              - Dov

     
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  • Currently Being Moderated
    Jun 14, 2012 4:01 PM   in reply to hariharan1986

    Then you will need to query the manufacturer of your multifunction device. It is not Adobe software that is generating that PDF file and we have no idea why they are doing what! Sorry!

     

              - Dov

     
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