DjVuLibRust

Rust library for encoding DjVu documents with a modern builder API. 100% working as of 1/2026.

Overview

DjVuLibRust provides a thread-safe, coordinate-based API for creating multi-page DjVu documents from image data. It supports out-of-order page processing, automatic layer masking, and optional parallel encoding.

Key Features

• Coordinate-based layers: Position image layers at specific coordinates with automatic JB2/IW44 masking
• Out-of-order processing: Add pages in any sequence, even in parallel
• Thread-safe: Safe concurrent access from multiple threads
• High performance: Optimized encoding with planned SIMD and assembly ZP coder support
• Memory efficient: Stream processing with minimal memory footprint
• Builder pattern: Intuitive API for complex document construction

Quick Start

use djvu_encoder::{DjvuBuilder, PageBuilder};

let doc = DjvuBuilder::new(10)
    .with_dpi(300)
    .with_quality(90)
    .build();

// Add pages (out-of-order supported)
for i in 0..10 {
    let page = PageBuilder::new(i, 2480, 3508)  // A4 @ 300dpi
        .with_background(load_pixmap(i))
        .with_foreground(load_bitmap(i), 50, 100)
        .build()?;
    doc.add_page(page)?;
}

let djvu_bytes = doc.finalize()?;
std::fs::write("output.djvu", djvu_bytes)?;

Image Formats

• Pixmap: RGB/grayscale images for IW44 background layers (photos, scans)
• Bitmap: Bilevel images for JB2 foreground layers (text, graphics)

Building

Prerequisites

• Rust 1.70+ (2024 edition)
• Cargo

Basic Build

cargo build --release

With Features

# Enable parallel processing
cargo build --release --features rayon

# Enable SIMD optimizations (planned - not yet finalized)
cargo build --release --features portable_simd

# Enable assembly ZP coder (planned - x86_64 only, not yet finalized)
cargo build --release --features asm_zp

# Enable IW44 debug tracing
cargo build --release --features iw44-trace

Feature Flags

Feature	Description	Default
rayon	Parallel encoding using Rayon	Disabled
portable_simd	SIMD optimizations for encoding (planned - not finalized)	Disabled
asm_zp	Assembly-optimized ZP arithmetic coder (planned - not finalized)	Disabled
iw44-trace	Verbose IW44 encoding debug output	Disabled
dev_asm_cmp	Assembly vs Rust ZP comparison tests	Disabled

Modules

• doc: Main builder API (DjvuBuilder, PageBuilder)
• encode: Core encoders
  • iw44: Wavelet compression for color/grayscale images
  • jb2: Bilevel compression for text/graphics
  • zc: Arithmetic coding backend
• iff: DjVu file format (IFF) handling
• image: Image types (Pixel, Pixmap, Bitmap) and operations
• annotations: DjVu annotation support
• utils: Error handling and utilities

Performance

• Parallel processing: Rayon-based multi-threading
• Memory efficient: Stream-based encoding with minimal allocations
• Planned optimizations: SIMD acceleration and assembly ZP coder (not yet finalized)

Compatibility

• Rust: 1.70+ (2024 edition)
• Platforms: Linux, macOS, Windows
• Architecture: x86_64, ARM64

License

Licensed under the GPL3 License. See LICENSE for details.

Contributing

Contributions welcome! Please see CONTRIBUTING.md for guidelines.

Related Projects

• Lege: PDF to DjVu converter using this library
• DjVuLibre: Reference DjVu implementation