leptonica-rs

A pure Rust reimplementation of the Leptonica image processing library — no C dependencies, cross-compile friendly, and unsafe-free.

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About Leptonica

Leptonica is an open-source C library for image processing and analysis, created and maintained by Dan Bloomberg. With approximately 240,000 lines of code and over 2,700 functions, it covers a broad range of operations from document image processing to natural image analysis. Leptonica has served as a foundational library for projects such as Tesseract OCR and OpenCV for over 20 years.

This project reimplements Leptonica's design and algorithms in Rust. The original C source code and documentation serve as the primary reference, included as a git submodule under reference/leptonica/.

Porting Status

Progress against the original 182 source files and 2,286 public functions.

Details: Feature comparison / Test comparison

Module Structure

Single crate leptonica with modules matching Leptonica's functional areas:

src/
├── lib.rs          # Public API entry (re-exports core types at root)
├── core/           # Base data structures (Pix, Box, Numa, FPix, Pta, Pixa, Colormap, SArray)
│   └── pixel.rs    # RGBA pixel ops (compose_rgba, extract_rgb, etc.)
├── io/             # Image I/O (PNG, JPEG, TIFF, BMP, GIF, WebP, PDF, PS)
├── transform/      # Geometric transforms (rotate, scale, affine, projective, bilinear)
├── morph/          # Morphological ops (dilate, erode, open, close, DWA, thinning)
├── filter/         # Filtering (convolve, bilateral, rank, edge, adaptmap)
├── color/          # Color processing (quantize, binarize, colorspace, segmentation)
├── region/         # Region analysis (conncomp, ccbord, quadtree, watershed, maze)
└── recog/          # Recognition (barcode, dewarp, baseline, pageseg, jbclass)

Build & Test

cargo check --all-features
cargo test
cargo test --all-features
cargo clippy --all-features --all-targets

Fetching the C Reference

git submodule update --init

Note: .gitmodules uses SSH URLs (git@github.com:...). If SSH keys are not configured, change the URL to HTTPS format.

Documentation

• CLAUDE.md -- Development conventions and process rules
• docs/plans/ -- Implementation plans for each feature
• docs/porting/ -- Porting reference materials (prompts, feature comparison, test comparison)

License

This project is distributed under the BSD 2-Clause License, the same license as the original Leptonica.

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.

This means the codebase may contain patterns that reflect AI-assisted development. Bug reports and feedback are welcome.

Acknowledgments

This project relies entirely on the source code, documentation, and regression tests of the original C Leptonica. It would not exist without the decades of design, implementation, and maintenance work by Dan Bloomberg and the Leptonica contributors.