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https://issues.apache.org/jira/browse/TIKA-4947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18125198#comment-18125198
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Tim Allison edited comment on TIKA-4947 at 10/8/26 6:30 PM:
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I looked around a bit and couldn't find anything that didn't cause more damage
than it helped.
I was particularly hopeful that PP-LCNet would work. But it did more harm than
just trusting an image was correctly oriented. The test set was rendered images
from the first pages of PDFs from digital corpora. I looked at 2k pages. There
were particular weaknesses with RTL language pages.
tesseract osd also does more harm than assuming a page is correctly aligned.
BUT, when it is run with OCR, it is quite accurate, at least on the files I ran
against. So, we can't run only orientation detection with tesseract and be
done. We could run tesseract with OCR and then extract orientation, but if
we're already running tesseract...
At this point, I think we have to rely on the vlm model to handle this. This is
not something that we can reliably fix before sending images off to models.
This answer does not bring me joy.
was (Author: [email protected]):
I looked around a bit and couldn't find anything that didn't cause more damage
than it helped.
I was particularly hopeful that PP-LCNet would work. But it was more wrong more
than right on rendered images from the first pages of PDFs from digital
corpora. I looked at 2k pages. There were particular weaknesses with RTL
language pages.
tesseract osd with only orientation detection is wrong more than it is right.
BUT, when it is run with OCR, it is quite accurate, at least on the files I ran
against. So, we can't run only orientation detection with tesseract and be done.
At this point, I think we have to rely on the vlm model to handle this. This is
not something that we can reliably fix before sending images off to models.
This answer does not bring me joy.
> Assess how we're doing with orientation detection for OCR
> ---------------------------------------------------------
>
> Key: TIKA-4947
> URL: https://issues.apache.org/jira/browse/TIKA-4947
> Project: Tika
> Issue Type: Task
> Reporter: Tim Allison
> Priority: Major
>
> Some vlm-based OCR tools are not robust against rotation and can hallucinate
> completely fluent content if an image is rotated.
> As with the blank image detection (TIKA-4946), I'm not sure if we put this in
> the PDFParser or the OCR engine or both.
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