Skip to content
Use case

Converting a Japanese PDF to EPUB

Updated:

Japanese text has no spaces between words, so joining lines and paragraphs needs different rules than Latin text. On a Japanese Wikipedia article the EPUBLab engine joins CJK lines without inserting spaces.

Original and result

CJK text without spaces between words, mixed with Latin script and numbers.

Original PDF
Page of the original PDF
Result (EPUB, as a reader shows it)
The same passage in the converted EPUB

Download source PDF Download the sample EPUB

Source and licence

Document
Wikipedia (Japanese): The Tale of Genji
Licence
CC BY-SA 4.0 (text); images under their own licences
Pages
67
Traits
text PDF, one column, Japanese, CJK

Settings used

  • Engine: epublab-core, build of 2026-11-03 (the one measured in the benchmark).
  • Pages: the whole document.
  • Options: none. The engine has no per-document settings yet; the same defaults apply to every file.

Validation and results

EPUBCheck EPUBCheck on our EPUB: 0 errors, 0 warnings.

8-gram recall · Like 4-gram recall with 8 words: drops when reading order or line joins break sentences (continuity). Methodology
Engine8-gram recall
EPUBLab engine (EPUB output)0.963
EPUBLab engine (plain text)0.963
pdf_oxide · extract_text0.970
pdf_oxide · to_plain_text (XY-cut)0.970
pdf_oxide · Markdown0.797
PDFium · text().all()0.952
OpenDataLoader PDF (local mode)0.942
pdftotext (Poppler)0.965

Limitations we observed

  • The source is horizontal text; vertical (tategaki) books have not been tested yet.
  • pdf_oxide and pdftotext score slightly higher than our engine on this document.

Convert a similar PDF