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https://issues.apache.org/jira/browse/TIKA-1994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15313972#comment-15313972
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Tim Allison commented on TIKA-1994:
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Sounds like a great strategy. That will catch image-only (or image-mostly)
pages. Let's open a separate issue to track other strategies beyond what I
initially put in.
bq. because it suggests a high chance that the page is formed by a big
(scanned) image
Note that we process the page and then run OCR (if the strategy is ocr+text).
We could gather info about the size/number of the images before making the
determination.
bq. speeds up the extraction a lot.
Y, I have to admit, I've been _really_ impressed by the quality of Tesseract
(on English, at least)...but the speed is an area of concern.
I'm hoping to run "ocr_only" against some of our corpus over the weekend and
compare that with "no_ocr." In addition to 'run ocr if there's only a little
text', it would be neat to be able to run ocr if there is 'bad text'
(TIKA-1443).
Have you done any experiments on dpi setting/image format/image type on OCR
performance? Does 200 dpi PNG GRAY do better than 200 dpi JPEG RGB...for
example?
> Integrate OCR with PDFParser
> ----------------------------
>
> Key: TIKA-1994
> URL: https://issues.apache.org/jira/browse/TIKA-1994
> Project: Tika
> Issue Type: Improvement
> Reporter: Tim Allison
> Assignee: Tim Allison
>
> Users can now run OCR on individual images embedded inline in PDFs if they
> get the configuration right.
> There are some drawbacks: 1) the text appears as an attachment if using the
> RecursiveParserWrapper, 2) text may be more cleanly extracted on the fully
> rendered page instead of on the individual images (this is still tbd).
> It might be useful to run OCR against each rendered page (instead of the
> component images).
> Integrating OCR is on the roadmap for PDFBox 2.1 (PDFBOX-1912). This will
> allow us to experiment with strategies until the cleaner integration is
> available with PDFBox 2.1.
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