Djvu-viewer

OsProject
edit
id	djvu-viewer
state	active
owner	WolfgangFahl
title	Djvu Viewer
url	https://github.com/WolfgangFahl/djvu-viewer
version	0.3.0
description	DjVu Viewer and tarball converter
date	2026-02-02
since	2026-02-01
until

Introduction

DjVu is a computer file format created by Léon Bottou and others with the goal to efficiently store scanned documents. At the time of its creation the priority was to save disk space and computer resources since these were precious and limited.

DjVu has elaborate mechanisms to provide this efficiency even to academic perfection. There is a tradeoff in this - DjVu files can only be processed with DjVu tools and there is basically only a single implementation available: DjvuLibre. The DjVuLibre git repository has not been touched for 8 years as of 2025 and it only has 23 stars. The original SourceForge repository https://djvu.sourceforge.net/ saw its latest release in 2020.

While DjVu is a great technology and a very useful special purpose solution, it is not optimal for modern AI pipelines and other applications where other aspects of processing play a more important role.

djvuconv therefore repackages DjVu files to tarballs including the lossless PNG version of each page - a "table of contents" in YAML format and optionally prepackaged thumbnails in JPEG format.

djvuconv is written in python but makes use of the original DjVuLibre library using the python-djvulibre library by Friedrich Fröbel which is a fork of the python-djvulibre library with Copyright © 2010-2021 Jakub Wilk <jwilk@jwilk.net> and GNU General Public License version 2 which was archive by Jakub in 2022.

Motivation

DjVu support in MediaWiki has been degrading over the past few years see

• wikimedia phabricator page
• DjVu thumbnails are not being generated at all
• Stackoverflow Question:DjVuImage::getMultiPageInfo: multi-page DJVU file contained no pages

Goals

• create a simple cross platform format for scanned documents
• use PNG, JPEG, PDF and YAML formats which have plenty of tools for viewing, processing and handling
• add native OCR support
• add native AI/LLM support

djvu catalog and remote viewer

RWTH Aachen

https://djvu-viewer.wikidata.dbis.rwth-aachen.de

• DjVu-Viewer
• AB1938_Heessen-Geschi.djvu tarball
• DjVu Wiki Images browser

RESTFul API

• https://djvu-viewer.wikidata.dbis.rwth-aachen.de/docs

CompGen e.V

https://genwiki39.genealogy.net/djvu-viewer/

• DjVu-Viewer
• AB1938_Heessen-Geschi.djvu tarball
• DjVu Wiki Images browser

RESTFul API

• https://genwiki39.genealogy.net/djvu-viewer//docs

Installation

pip install djvu-viewer
# alternatively if your pip is not a python3 pip
pip3 install djvu-viewer 
# local install from source directory of djvu-viewer 
pip install .

upgrade

pip install djvu-viewer  -U
# alternatively if your pip is not a python3 pip
pip3 install djvu-viewer -U

Command Line

djvuconv

djvuconv converts collection of DjVu files to tarballs. It create optionally collects the metadata which may be stored in a database for further analysis and processing.

Command Line Usage

djvuconv -h
usage: djvuconv [-h] [--base-path BASE_PATH] [--batch-size BATCH_SIZE]
                --command {catalog,convert,thumbnails,dbupdate} [-d]
                [--db-path DB_PATH] [-f] [--limit LIMIT]
                [--max-errors MAX_ERRORS] [--max-workers MAX_WORKERS]
                [--output-path OUTPUT_PATH] [--serial] [--sort {asc,desc}]
                [-v] [--url URL]

Process DjVu files

options:
  -h, --help            show this help message and exit
  --base-path BASE_PATH
                        Base path for DjVu files
  --batch-size BATCH_SIZE
                        Number of pages to process in each batch (default:
                        100)
  --command {catalog,convert,thumbnails,dbupdate}
                        Command to execute
  -d, --debug           Enable debugging
  --db-path DB_PATH     Path to the database
  -f, --force           Force recreation
  --limit LIMIT         Maximum number of pages to process
  --max-errors MAX_ERRORS
                        Maximum allowed error percentage before skipping
                        database update
  --max-workers MAX_WORKERS
                        Maximum number of worker threads (default: CPU count *
                        4)
  --output-path OUTPUT_PATH
                        Path for PNG files
  --serial              Use serial processing - parallel is default
  --sort {asc,desc}     Sort by page count (asc=smallest first)
  -v, --verbose         Enable debugging
  --url URL             Process a single DjVu file (only valid in convert
                        mode)

Server configuration

Apache proxy

# Apache Configuration for djvu.bitplan.com
# WF 2026-02-02
# http Port: 9840
# SSL Port: 443
# 
# timeout: 3.0
<VirtualHost *:443>
    ServerName djvu.bitplan.com
    ServerAdmin webmaster@bitplan.com

    Include ssl.conf
    ErrorLog ${APACHE_LOG_DIR}/djvu_error_ssl.log
    CustomLog ${APACHE_LOG_DIR}/djvu_ssl.log combined

    RewriteEngine On
    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteRule /(.*) ws://localhost:9840/$1 [P,L]
    RewriteCond %{HTTP:Upgrade} !=websocket [NC]
    RewriteRule /(.*) http://localhost:9840/$1 [P,L]

    ProxyPassReverse / http://localhost:9840/
</VirtualHost>
<VirtualHost *:80>
    ServerName djvu.bitplan.com
    ServerAdmin webmaster@bitplan.com

    
    ErrorLog ${APACHE_LOG_DIR}/djvu_error.log
    CustomLog ${APACHE_LOG_DIR}/djvu.log combined

    RewriteEngine On
    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteRule /(.*) ws://localhost:9840/$1 [P,L]
    RewriteCond %{HTTP:Upgrade} !=websocket [NC]
    RewriteRule /(.*) http://localhost:9840/$1 [P,L]

    ProxyPassReverse / http://localhost:9840/
</VirtualHost>

Caddy proxy

 # Djvu-Viewer (NiceGUI on 9840), mounted at /djvu-viewer/
   # Strip the prefix for the upstream and tell it where it's mounted.
   handle_path /djvu-viewer/* {
     reverse_proxy http://localhost:9840 {
       header_up Host {host}
       header_up X-Forwarded-Host {host}
       header_up X-Forwarded-Proto {scheme}
       header_up X-Forwarded-Prefix /djvu-viewer
       # WebSocket Origin enforcement
       header_up Origin {scheme}://{host}
      }
    }

Catalog database structure

YAML

AB1938_Kreis-Beckum_Inhaltsverz

Note: the bundled flag might be wrong in some of our demos - the bundle state can be determined from all djvu_path being identical

path: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu
page_count: 3
bundled: false
pages:
- path: AB1938 Kreis-Beckum_Titel_0001.djvu
  page_index: 1
  valid: false
  width: 2105
  height: 1511
  dpi: 300
  djvu_path: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu
  page_key: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu#0001
- path: s003_0001.djvu
  page_index: 2
  valid: false
  width: 2089
  height: 2742
  dpi: 300
  djvu_path: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu
  page_key: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu#0002
- path: s004_0001.djvu
  page_index: 3
  valid: false
  width: 2057
  height: 1943
  dpi: 300
  djvu_path: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu
  page_key: /images/c/c7/AB1938_Kreis-Beckum_Inhaltsverz.djvu#0003

AB1932-Ramrath

path: /images/f/ff/AB1932-Ramrath.djvu
page_count: 2
bundled: true
pages:
- path: AB1932-Ramrath_s274_0001.djvu
  page_index: 1
  valid: false
  width: 761
  height: 2341
  dpi: 300
  djvu_path: /images/f/ff/AB1932-Ramrath.djvu
  page_key: /images/f/ff/AB1932-Ramrath.djvu#0001
- path: AB1932-Ramrath_s275_0001.djvu
  page_index: 2
  valid: false
  width: 1386
  height: 2306
  dpi: 300
  djvu_path: /images/f/ff/AB1932-Ramrath.djvu
  page_key: /images/f/ff/AB1932-Ramrath.djvu#0002

Plauen-AB-1938

path: /images/c/ce/Plauen-AB-1938.djvu
page_count: 2
bundled: true
pages:
- path: BaEVKcJP5e.djvu
  page_index: 1
  valid: false
  width: 685
  height: 1049
  dpi: 72
  djvu_path: /images/c/ce/Plauen-AB-1938.djvu
  page_key: /images/c/ce/Plauen-AB-1938.djvu#0001
- path: y4RN9G4reI.djvu
  page_index: 2
  valid: false
  width: 725
  height: 1031
  dpi: 72
  djvu_path: /images/c/ce/Plauen-AB-1938.djvu
  page_key: /images/c/ce/Plauen-AB-1938.djvu#0002

SQL

DjVu

CREATE TABLE DjVu (
  path TEXT PRIMARY KEY,
  page_count INTEGER,
  bundled BOOLEAN,
  iso_date TEXT,
  filesize INTEGER,
  tar_iso_date TEXT,
  tar_filesize INTEGER
)

Page

CREATE TABLE Page (
  path TEXT,
  page_index INTEGER,
  valid BOOLEAN,
  width INTEGER,
  height INTEGER,
  dpi INTEGER,
  djvu_path TEXT,
  page_key TEXT PRIMARY KEY
)