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nweddington
Participant
September 11, 2025
Answered

Images that are part of an object group are rendered as blocky and grayish

  • September 11, 2025
  • 1 reply
  • 361 views

Images that are part of an object group render the image as blocky and grayish on some PDF files despite the fact any PDF rendering engine in Chrome, Firefox, or Edge render the PDF documents correctly.  I copied multipe instance of object groups with images that display this problem into one test.pdf document which displays the same problem on multiple computer with the latest version of Acrobat installed.  I then printed the problematic test.pdf file using firefox to save it as a new PDF (test2.pdf) which then displays correctly in Acrobat.  Why can't Acrobat display these images correctly in the original PDF when other PDF rendering engines can?

    Correct answer nweddington

    Hi there, 

     

    Thanks for sharing these details. Since the PDFs are older and coming directly from the journal’s website, it makes sense that you wouldn’t be able to modify them. What you’re noticing could indeed be related to compatibility changes in Acrobat over time. Some older PDFs may contain elements or structures that newer versions of Acrobat interpret differently, which can sometimes cause rendering issues that weren’t present years ago.

     

    Would you mind sharing an affected PDF file so we can check it at our end? This way, we can test the file and confirm if this is a regression bug and isolate this issue for the fix. 

     

    ~Amal


    Someone must have fixed it as all the computers that previoulsly had the problem are now displaying the files correctly.  Thanks for the help everyone.

    1 reply

    kglad
    Community Expert
    kgladCommunity Expert
    Community Expert
    September 11, 2025

    in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

    p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.



    <"moved from using the community bugs">
    Amal.
    Amal.
    Legend
    September 12, 2025

    Hi there,

     

    Hope you are doing well and thanks for bringing this up.

    What you’re seeing is likely related to how Acrobat’s rendering engine interprets certain object groups with embedded images. Different viewers (like Chrome, Firefox, and Edge) use their own PDF rendering engines, which can sometimes process non-standard or complex objects differently than Acrobat does. That’s why the same file may look fine in one viewer but appear blocky or grayish in Acrobat.

     

    Since re-printing through Firefox resolves the issue, it suggests the images are being flattened or re-encoded in a way that Acrobat can read without issue. The original file may contain transparency, layering, or encoding that Acrobat doesn’t handle as smoothly.

     

    Here are a few things you can try:

    • Preflight or optimize the PDF: Use Acrobat’s “Preflight” or “Save as Optimized PDF” to flatten transparencies or re-encode images https://adobe.ly/4nx61m7  and https://adobe.ly/48dVJmg 

    • Try different creation settings: If you have control over how the original PDF is generated, adjusting export settings (for images, transparency, or compatibility level) can help.

     

    ~Amal

      N
      nweddingtonAuthor
      Participant
      September 12, 2025

      Thanks you for your response.  All of the files that have this issue are older PDFs (2006 and 2009) that were submitted to scientific journals by faculty, I don't think they can be changed now and are being downloaded directly from the journal's web site.  Also, I don't think Acrobat had this rendering problem with the files back when they were created years ago or the researchers wouldn't have submitted those versions of their papers.  To me it seems like a bug and I think that Acrobat should be able to render them correctly without having to modify the files.

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