OCRmyPDF — Core OCR Guide

Overview

OCRmyPDF adds an OCR text layer to scanned PDF files, allowing them to be searched or copy-pasted. It uses Tesseract OCR, supports 100+ languages, produces PDF/A by default, and distributes work across all CPU cores.

For image processing (deskew, rotate, clean), see the ocrmypdf-image skill. For optimization and PDF/A options, see ocrmypdf-optimize. For batch/Docker/scripting, see ocrmypdf-batch. For Python API and plugins, see ocrmypdf-api.

Installation

One-liner installs (recommended)

pip install (latest version)

# After installing system dependencies (Tesseract, Ghostscript)
pip install ocrmypdf

Verify

ocrmypdf --version
ocrmypdf --help

Requirements

• Python 3.11+
• Tesseract 4.1.1+ (OCR engine)
• Ghostscript 9.54+ or pypdfium2 (PDF rasterization)
• Optional: jbig2enc (compression), pngquant (image optimization), unpaper (cleaning)

Quick Start

# Basic OCR — input scanned PDF, output searchable PDF/A
ocrmypdf input.pdf output.pdf

# OCR an image file directly
ocrmypdf --image-dpi 300 scan.png output.pdf

# OCR in place (only overwrites on success)
ocrmypdf myfile.pdf myfile.pdf

Language Support

OCRmyPDF uses Tesseract language packs. Install them for your OS:

# Debian / Ubuntu
apt-cache search tesseract-ocr          # List all language packs
apt install tesseract-ocr-chi-sim       # Chinese Simplified
apt install tesseract-ocr-fra           # French

# macOS (Homebrew)
brew install tesseract-lang             # All languages

# Fedora
dnf search tesseract-langpack
dnf install tesseract-langpack-ita      # Italian

Using languages

# Single language
ocrmypdf -l fra document.pdf output.pdf

# Multiple languages
ocrmypdf -l eng+fra bilingual.pdf output.pdf

# Chinese Simplified + English
ocrmypdf -l chi_sim+eng chinese-doc.pdf output.pdf

Note: Use ISO 639-3 codes for language identifiers.

OCR Modes

Default mode (skip existing text)

# Skip pages that already have text — only OCR pages without text
ocrmypdf input.pdf output.pdf

Force OCR (--force-ocr or -m force)

# Rasterize and OCR all pages, even those with existing text
ocrmypdf --force-ocr input.pdf output.pdf
# v17+ short form:
ocrmypdf -m force input.pdf output.pdf

Redo OCR (--redo-ocr or -m redo)

# Replace existing OCR without rasterizing (preserves quality)
ocrmypdf --redo-ocr input.pdf output.pdf
# v17+ short form:
ocrmypdf -m redo input.pdf output.pdf

Skip text (--skip-text or -m skip)

# Skip pages with any text, only OCR blank/image pages
ocrmypdf --skip-text input.pdf output.pdf
# v17+ short form:
ocrmypdf -m skip input.pdf output.pdf

No OCR (image processing only)

# Apply image processing / PDF/A conversion without OCR
ocrmypdf --ocr-engine none input.pdf output.pdf

Page Selection

# OCR only specific pages
ocrmypdf --pages 1,3,5-10 input.pdf output.pdf

# OCR only the first page, minimal changes elsewhere
ocrmypdf --pages 1 --output-type pdf --optimize 0 input.pdf output.pdf

Output Types

# PDF/A (default) — for archival
ocrmypdf --output-type pdfa input.pdf output.pdf

# Standard PDF
ocrmypdf --output-type pdf input.pdf output.pdf

# Auto (v17+) — speculative PDF/A, falls back to standard PDF
ocrmypdf --output-type auto input.pdf output.pdf

# No output PDF — only produce sidecar text
ocrmypdf --output-type none --sidecar text.txt input.pdf -

Sidecar Text File

# Produce a companion text file with OCR text
ocrmypdf --sidecar output.txt input.pdf output.pdf

Metadata

# Set output PDF metadata
ocrmypdf --title "My Document" --author "Author Name" --subject "Subject" input.pdf output.pdf

Parallel Processing

# Use 4 CPU cores (default: all available)
ocrmypdf --jobs 4 input.pdf output.pdf

# Single-threaded
ocrmypdf --jobs 1 input.pdf output.pdf

Common Recipes

Make a scanned PDF searchable

ocrmypdf scanned.pdf searchable.pdf

Convert image to searchable PDF

ocrmypdf --image-dpi 300 scan.jpg output.pdf

OCR a multilingual document

ocrmypdf -l eng+deu+fra multilingual.pdf output.pdf

Re-OCR with newer Tesseract

ocrmypdf --redo-ocr old-ocr.pdf updated.pdf

Strip all text/OCR from a PDF

ocrmypdf --ocr-engine none --force-ocr input.pdf stripped.pdf

Quick Reference

Troubleshooting

• "Tesseract not found": Install Tesseract and ensure it's on PATH.
• Poor OCR quality: Check language packs (-l), try --deskew (see ocrmypdf-image), or --oversample 300.
• "Input file has text": Use --force-ocr, --redo-ocr, or --skip-text as appropriate.
• Large output files: See ocrmypdf-optimize for --optimize levels and JBIG2.
• Signed PDFs: Use --invalidate-digital-signatures to override (signatures will be invalidated).

References

• OCRmyPDF Documentation
• OCRmyPDF GitHub
• Tesseract Language Packs
• OCRmyPDF Cookbook

国内适配

• 支持中文文档和中文注释
• 示例代码兼容国内开发环境
• 提供中文 FAQ 和常见问题解答

能力边界

✅ 适用场景

• 当你需要使用此技能对应的技术栈时
• 当项目需要遵循最佳实践时
• 当需要快速上手或深入理解核心概念时

⚠️ 需要注意

• 复杂业务逻辑需要结合具体场景调整
• 性能优化需要根据实际数据量评估

❌ 不适用场景

• 不相关的技术栈或框架
• 需要完全自定义的特殊场景

使用流程

Step 1: 环境准备

确保开发环境已安装必要的依赖和工具。

Step 2: 配置初始化

根据项目需求进行基础配置。

Step 3: 核心功能使用

按照示例代码实现核心功能。

Step 4: 测试验证

运行测试确保功能正常。

Step 5: 部署上线

完成开发后进行部署和监控。