jbig2enc

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A Rust reimplementation of jbig2enc, a JBIG2 encoder for bi-level (1 bpp) images.

JBIG2 is a compression standard for bi-level images that achieves better compression ratios than G4 (CCITT Group 4) through symbol extraction and dictionary-based reuse. It is commonly used for embedding scanned document images into PDFs.

This crate provides both a library API and a command-line tool. Written entirely in Rust with no C/C++ dependencies -- the image processing foundation leptonica is also a pure Rust reimplementation, so the entire toolchain builds with cargo alone.

Installation

Library

[dependencies]
jbig2enc = "0.1"

To use only as a library without the CLI binary:

[dependencies]
jbig2enc = { version = "0.1", default-features = false }

CLI

cargo install jbig2enc

Library Usage

Single-page lossless encoding (generic region):

use jbig2enc::encoder::encode_generic;
use leptonica::io::read_image;

let pix = read_image("input.png").unwrap();
let data = encode_generic(&pix, true, 300, 300, false).unwrap();
std::fs::write("output.jbig2", &data).unwrap();

Multi-page symbol mode encoding:

use jbig2enc::encoder::Jbig2Context;
use leptonica::io::read_image;

let mut ctx = Jbig2Context::new(0.92, 0.5, 300, 300, true, -1).unwrap();
let page = read_image("page1.png").unwrap();
ctx.add_page(&page).unwrap();

let symbol_table = ctx.pages_complete().unwrap();
let page_data = ctx.produce_page(0, None, None).unwrap();

Modules

• arith -- QM arithmetic coder, the core entropy coding engine
• comparator -- Symbol template equivalence detection
• encoder -- Multi-page compression context and generic region encoding
• error -- Error types
• symbol -- Symbol dictionary and text region encoding
• wire -- JBIG2 wire format structures

CLI Usage

# Single-page generic encoding (output to stdout)
jbig2enc input.png > output.jbig2

# Symbol mode with PDF-ready output
jbig2enc -s -p input.png

# Multi-page symbol mode
jbig2enc -s -p page1.png page2.png page3.png

# With duplicate line removal
jbig2enc -d input.png > output.jbig2

# Custom threshold and DPI
jbig2enc -s -p -t 0.85 -D 300 input.png

Run jbig2enc --help for the full list of options.

Feature Flags

Minimum Supported Rust Version

Rust 2024 edition (1.87+).

License

This project is distributed under the Apache License 2.0, the same license as the original jbig2enc.

Acknowledgments

This project relies on the source code and design of the original C++ jbig2enc by Adam Langley. It also depends on leptonica as its image processing foundation, which in turn is a reimplementation of Leptonica by Dan Bloomberg.

How This Project Is Built

The porting work is carried out primarily by AI coding agents, including Claude Code. A human maintainer defines the overall architecture, process rules, and acceptance criteria, while the agents read the original C++ source, write Rust code, and run tests under those constraints. Every commit goes through CI and automated review before merging.