OCRmyPDF — Optimization Guide

Overview

OCRmyPDF provides extensive optimization options to reduce file size, create PDF/A archival documents, and configure output quality.

For core OCR functionality, see the ocrmypdf skill. For image processing (deskew, rotate, clean), see ocrmypdf-image. For batch/Docker/scripting, see ocrmypdf-batch.

Compression Levels

# Level 0 — no optimization (fastest)
ocrmypdf --optimize 0 input.pdf output.pdf

# Level 1 — lossless (default)
ocrmypdf --optimize 1 input.pdf output.pdf

# Level 2 — lossy (aggressive)
ocrmypdf --optimize 2 input.pdf output.pdf

# Level 3 — lossless, aggressive JPEG recompression
ocrmypdf --optimize 3 input.pdf output.pdf

PDF/A Output

PDF/A is an archival format with embedded fonts and colorspaces:

# PDF/A-1b (basic, default)
ocrmypdf --output-type pdfa input.pdf output.pdf

# PDF/A-2b (includes transparency)
ocrmypdf --output-type pdfa2b input.pdf output.pdf

# PDF/A-2u (Unicode)
ocrmypdf --output-type pdfa2u input.pdf output.pdf

# Standard PDF (no archival)
ocrmypdf --output-type pdf input.pdf output.pdf

JBIG2 Encoding

JBIG2 provides excellent compression for monochrome (1-bit) images:

# Enable JBIG2 (requires jbig2enc)
ocrmypdf --jbig2-lossy input.pdf output.pdf  # Lossy

ocrmypdf --jbib2-lossless input.pdf output.pdf  # Lossless (v17+)

Requirements:

# Debian/Ubuntu
apt install jbig2enc

# macOS
brew install jbig2enc

PNG Optimization

Optimize embedded PNG images:

# Use pngquant for lossy compression
ocrmypdf --png-lossy input.pdf output.pdf

# Lossless PNG optimization
ocrmypdf --png-lossless input.pdf output.pdf

Ghostscript Options

Fine-tune PDF processing with Ghostscript:

# Set PDF minor version
ocrmypdf --pdf-renderer hatch input.pdf output.pdf

# Use pdfimages for better image extraction
ocrmypdf --pdf-renderer img2pdf input.pdf output.pdf

Sidecar Text

Generate text file alongside PDF without modifying PDF:

# Generate sidecar only
ocrmypdf --output-type none --sidecar text.txt input.pdf output.pdf

# Typical sidecar workflow
ocrmypdf --sidecar text.txt --force-ocr input.pdf output.pdf

Combined Recipes

Maximum compression

ocrmypdf --optimize 3 --jbig2-lossy --png-lossy input.pdf small.pdf

Archival PDF/A with compression

ocrmypdf --output-type pdfa --optimize 2 input.pdf archival.pdf

Lossless output

ocrmypdf --output-type pdf --optimize 1 --png-lossless input.pdf lossless.pdf

Quick Reference

Task	Command
No optimization	--optimize 0
Lossless default	--optimize 1
Aggressive lossy	--optimize 2
Max quality	--optimize 3
PDF/A-1b (default)	--output-type pdfa
PDF/A-2b	--output-type pdfa2b
JBIG2 lossy	--jbig2-lossy
PNG lossy	--png-lossy
Sidecar text	--sidecar text.txt

Troubleshooting

• Large file size: Try --optimize 2 or --png-lossy.
• PDF/A validation fails: Use --output-type pdfa2b for better compatibility.
• Font issues: PDF/A-2u ensures full Unicode support.