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https://issues.apache.org/jira/browse/PDFBOX-1912?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15836632#comment-15836632
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Tim Allison commented on PDFBOX-1912:
-------------------------------------
Y, thank you, [~tilman]. We have two basic strategies. One runs OCR on
extracted inline images one by one, and the other uses PDFBox to render each
page and then runs Tesseract on the full image. Let us know if/when you have
questions.
See our general [OCR wiki page|https://wiki.apache.org/tika/TikaOCR] and our
[PDF-specific
notes|https://wiki.apache.org/tika/PDFParser%20%28Apache%20PDFBox%29#OCR]
> Optical Character Recognition (OCR)
> -----------------------------------
>
> Key: PDFBOX-1912
> URL: https://issues.apache.org/jira/browse/PDFBOX-1912
> Project: PDFBox
> Issue Type: New Feature
> Components: Text extraction
> Affects Versions: 2.0.0
> Environment: JDK 6, C/C++
> Reporter: John Hewson
> Assignee: John Hewson
> Labels: gsoc2014
> Fix For: 2.1.0
>
>
> Brief explanation: The PDFBox library is widely used to extract text from PDF
> files. However, many PDF files embed text in a malformed manner which renders
> text extraction useless. There has recently been interest in extracting
> governmental data from PDF files, the PDF Liberation commons being a notable
> example, see https://github.com/pdfliberation for more details.
> Many end-users of PDFBox have been making use of OCR tools such as Google's
> Tesseract https://code.google.com/p/tesseract-ocr/ which are run on the final
> image generated by PDFBox. We think that by adding a more integrated OCR API
> to PDFBox it will be possible to do a better job. PDFBox often has access to
> encoding and positioning information for individual glyphs. Even when their
> extracted text is meaningless, a character-by-character, or line-by-line OCR
> could be more accurate. PDFBox also has information such as image orientation
> which could allow it to better perform OCR on pages such as embedded
> landscape tables.
> There are existing JNI bindings for Tesseract available at
> https://code.google.com/p/tesseract-android-tools/
> Expected results: To extend PDF box with an API which allows external OCR
> tools to be plugged-in, and an implementation of a Tesseract plug-in using
> either JNI or the command line via Process.exec.
> Knowledge Prerequisite: Java, JNI (C/C++)
> Mentor: John Hewson
> PMC Note: Tesseract is under the Apache License 2.0
> To learn more about PDFBox, please visit http://pdfbox.apache.org/
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