Light Novel Scan -> EPUB

Turns a folder of scanned light novel page images (vertical Japanese text) into a proper .epub, with furigana rendered as real <ruby> markup, illustrations kept in place, an embedded font, and epub metadata — using a multimodal LLM to do the OCR instead of a traditional column-segmentation pipeline.

Pipeline

scanned page images
        │
        ▼
   ocr/ module          → transcribes each page into pages_txt/<name>.txt
        │
        ▼
  (manual step)          → sort the .txt files (and any illustration
                            images) into chapters/chNN_name/ folders
        │
        ▼
epub_builder/ module     → assembles chapters/ into a finished .epub

ocr/ — batch-OCRs scanned pages into per-page .txt files. Several backends are available (a multimodal LLM via any OpenAI-compatible API is the recommended default; Google Cloud Vision and a fully offline manga-ocr pipeline are also included).
Manual sorting — split the resulting pages into chapter folders (ch00_frontmatter/, ch01_chapter00/, ...), optionally dropping in a cover.jpg and illustration images alongside the .txt files. This step is manual because automatically detecting chapter boundaries from OCR'd headers turned out to be unreliable — folder structure is simple and unambiguous instead.
epub_builder/ — assembles the sorted chapters/ folder into a valid .epub: furigana notation becomes <ruby> markup, images are placed inline, a font from font/ gets embedded, and metadata comes from config.json.

See each module's own README for setup and usage details.

Quick start

# 1. OCR
cd ocr
pip install openai pillow natsort tqdm
cp config.example.json config.json   # fill in api_key / base_url / model
python openrouter_ocr.py --input /path/to/scans --output ./out

# 2. Sort ./out/pages_txt/*.txt by hand into epub_builder/chapters/chNN_name/

# 3. Build the epub
cd ../epub_builder
pip install natsort
cp config.example.json config.json   # fill in title / author / ...
python build_epub.py

⚠️ A note on copyright

This repository contains only the tooling. It is not meant to, and should not, be used to host or distribute:

scanned page images,
OCR'd text extracted from a copyrighted book,
or a resulting .epub file,

for any book you don't hold the rights to. The .gitignore in this repo already excludes chapters/, pages_txt/, out/, and *.epub for this reason — keep it that way if you fork or extend this project. This tool is intended for personal-use digitization of books you own, not redistribution.

Requirements

See requirements.txt for the full list. Not every dependency is needed at once — install only what the OCR backend and features you're using require (see each module's README).

Status

This is a personal toolkit, still evolving. Contributions/forks welcome, but expect rough edges — issues and PRs are handled best-effort.

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