OCR Document Scanning

DocuDesk integrates Tesseract OCR to extract searchable text from scanned documents and image-based files. OCR is transparent to the rest of the pipeline — once text is extracted, it feeds into the existing entity detection and anonymization workflows.

Overview

The OCR feature:

1. Detects whether a file needs OCR (image-based or text-less PDF)
2. Extracts text using Tesseract (configurable languages and DPI)
3. Returns the extracted text for downstream processing (entity detection, anonymization)
4. Degrades gracefully when Tesseract is not installed — the service reports unavailability rather than crashing

Supported File Types

Images

• image/png
• image/jpeg
• image/jpg
• image/tiff
• image/bmp
• image/gif
• image/webp

PDFs

• application/pdf — when the PDF contains no embedded text (i.e. a scanned PDF)

API Endpoints

OCR processing is exposed through the document processing pipeline. The OcrService is invoked automatically by DocumentTextExtractor when it encounters an image or text-less PDF.

Direct OCR triggering uses the standard file processing endpoint:

POST /apps/docudesk/api/anonymization/extract/{fileId}

The response includes an ocrApplied: true flag when OCR was used.

Configuration Options

Configured via the DocuDesk admin settings page or occ config:app:set:

Config key	Default	Description
docudesk_ocr_enabled	true	Enable or disable OCR processing globally
docudesk_ocr_languages	nld+eng	Tesseract language codes (e.g. nld+eng+fra)
docudesk_ocr_dpi	300	Resolution for image extraction (higher = better quality, slower)

Setting OCR Language

docker exec nextcloud php occ config:app:set docudesk docudesk_ocr_languages --value="nld+eng+fra"

Available language packs depend on which Tesseract language data files are installed in the container. Install via apt-get install tesseract-ocr-nld tesseract-ocr-eng.

Installation Requirements

Tesseract OCR must be installed on the Nextcloud host or container:

apt-get install tesseract-ocr tesseract-ocr-nld tesseract-ocr-eng

The service checks for Tesseract availability on each call to isTesseractAvailable(). If Tesseract is missing, processing continues without OCR and returns empty text rather than throwing.

Services

OcrService

Main OCR service.

Method	Description
isTesseractAvailable()	Check whether the Tesseract binary is available on the system
getTesseractVersion()	Return the installed Tesseract version string, or null
needsOcr()	Determine if a file type/content requires OCR
isOcrEnabled()	Check whether OCR is enabled in app configuration
getOcrLanguages()	Return the configured Tesseract language string
getOcrDpi()	Return the configured scan DPI
extractTextFromImage()	Run Tesseract on a Nextcloud File object of image type
extractTextFromPdf()	Run Tesseract on each page of a scanned PDF
processFile()	Determine file type, apply OCR if needed, return extracted text and metadata

Integration with Text Extraction

DocumentTextExtractor calls OcrService::processFile() when a file cannot yield text through standard means (e.g. pdftotext). The extracted text is then passed to EntityDetectionService for NER analysis.

Dependencies

Dependency	Purpose
thiagoalessio/tesseract-ocr	PHP wrapper around the Tesseract binary
OCP\Files\IRootFolder	Access Nextcloud files by file ID
OCP\IAppConfig	Read OCR configuration settings
OCP\IUserSession	Determine current user for file access