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extract_text doesn't extract ligatures correctly #598

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Baytars opened this issue Jan 25, 2021 · 4 comments
Closed

extract_text doesn't extract ligatures correctly #598

Baytars opened this issue Jan 25, 2021 · 4 comments
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is-bug From a users perspective, this is a bug - a violation of the expected behavior with a compliant PDF PdfReader The PdfReader component is affected workflow-text-extraction From a users perspective, text extraction is the affected feature/workflow

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@Baytars
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Baytars commented Jan 25, 2021 •
edited

I appreciate it that your tool keep the original reading order of text and omit those repeated headers and footers that interfere with main body text that crosses pages, which makes conversion from PDF to EPUB convenient. However, there seems to be a gremlin for the extracted text - some strings are misreplaced by some punctuation marks, like

  • fi misreplaced by ˛ (e.g. fields extracted to be ˛elds)
  • ff misreplaced by ˙ or ˜ (e.g. different extracted to be di˙erent and Differential extracted to be Di˜erential)
  • ft misreplaced by ˚ (e.g. after extracted to be a˚er)
  • th misreplaced by ˜ (e.g. this extracted to be ˜is)
    For comparison I used Python pdftotext package too and found out there's no such a problem, but that package keep the original typography which puts two columns of texts in a row and is not ideal for PDF conversion.
    Any clue about this issue? Looking forward to a perfect PyPDF because it is so useful!
@MartinThoma
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#464 might solve this

@MartinThoma MartinThoma added is-bug From a users perspective, this is a bug - a violation of the expected behavior with a compliant PDF PdfReader The PdfReader component is affected labels Apr 8, 2022
@MartinThoma MartinThoma added the workflow-text-extraction From a users perspective, text extraction is the affected feature/workflow label Apr 16, 2022
@MartinThoma
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#924 very likely fixed it. It looks as if you might have seen issues with cmaps / ligatures.

PyPDF2==2.1.0 should no longer have this issue. I'll release it today.

@MartinThoma MartinThoma changed the title Misreplaced extracted text extract_text doesn't extract ligatures correctly Jun 6, 2022
MartinThoma added a commit that referenced this issue Jun 6, 2022
@MartinThoma
REL: 2.1.0
4e44122 
The highlight of the 2.1.0 release is the most massive improvement to the
text extraction capabilities of PyPDF2 since 2016 🥳🎊 A very big thank you goes
to [pubpub-zz](https://github.com/pubpub-zz) who took a lot of time and
knowledge about the PDF format to finally get those improvements into PyPDF2.
Thank you 🤗💚

In case the new function causes any issues, you can use `_extract_text_old`
for the old functionality. Please also open a bug ticket in that case.

There were several people who have attempted to bring similar improvements to
PyPDF2. All of those were valuable. The main reason why they didn't get merged
is the big amount of open PRs / issues. pubpub-zz was the most comprehensive
PR which also incorporated the latest changes of PyPDF2 2.0.0.

Thank you to [VictorCarlquist](https://github.com/VictorCarlquist) for #858 and
[asabramo](https://github.com/asabramo) for #464 🤗

New Features (ENH):
-  Massive text extraction improvement (#924). Closed many open issues:
    - Exceptions / missing spaces in extract_text() method (#17) 🕺
      - Whitespace issues in extract_text() (#42) 💃
      - pypdf2 reads the hifenated words in a new line (#246)
    - PyPDF2 failing to read unicode character (#37)
      - Unable to read bullets (#230)
    - ExtractText yields nothing for apparently good PDF (#168) 🎉
    - Encoding issue in extract_text() (#235)
    - extractText() doesn't work on Chinese PDF (#252)
    - encoding error (#260)
    - Trouble with apostophes in names in text "O'Doul" (#384)
    - extract_text works for some PDF files, but not the others (#437)
    - Euro sign not being recognized by extractText (#443)
    - Failed extracting text from French texts (#524)
    - extract_text doesn't extract ligatures correctly (#598)
    - reading spanish text - mark convert issue (#635)
    - Read PDF changed from text to random symbols (#654)
    - .extractText() reads / as 1. (#789)
-  Update glyphlist (#947) - inspired by #464
-  Allow adding PageRange objects (#948)

Bug Fixes (BUG):
-  Delete .python-version file (#944)
-  Compare StreamObject.decoded_self with None (#931)

Robustness (ROB):
-  Fix some conversion errors on non conform PDF (#932)

Documentation (DOC):
-  Elaborate on PDF text extraction difficulties (#939)
-  Add logo (#942)
-  rotate vs Transformation().rotate (#937)
-  Example how to use PyPDF2 with AWS S3 (#938)
-  How to deprecate (#930)
-  Fix typos on robustness page (#935)
-  Remove scripts (pdfcat) from docs (#934)

Developer Experience (DEV):
-  Ignore .python-version file
-  Mark deprecated code with no-cover (#943)
-  Automatically create Github releases from tags (#870)

Testing (TST):
-  Text extraction for non-latin alphabets (#954)
-  Ignore PdfReadWarning in benchmark (#949)
-  writer.remove_text (#946)
-  Add test for Tree and _security (#945)

Code Style (STY):
-  black, isort, Flake8, splitting buildCharMap (#950)

Full Changelog: 2.0.0...2.1.0
@gargarvin
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gargarvin commented Sep 16, 2022 •
edited

I am still having this issue.
'fi' 'fl' and 'ff' characters are returning NULL

PDF

@MartinThoma MartinThoma reopened this Sep 17, 2022
@pubpub-zz
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We can leave it closed: @gargarvin opened #1351 for the new test case

@MartinThoma MartinThoma mentioned this issue Sep 18, 2022
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