DjVu

DjVu is a computer file format designed for the storage of scanned documents, particularly those that combine text, line drawings, and photographs. It aims to deliver high compression while preserving legibility, making it well suited for digitized books, magazines, and archival materials.

The format uses a page as multiple image layers: a background layer for smooth areas, a foreground layer for text and fine line art, and a binary mask that separates the foreground from the background. This separation allows each layer to be compressed with the most appropriate method, often yielding much smaller files than equivalent TIFF or PDF scans. DjVu pages may also include a text layer produced by OCR, enabling searchable text, as well as metadata and document structure information. DjVu supports color and grayscale, and multi-page documents.

Implementation and ecosystem. The open-source DjVuLibre project provides libraries and tools for creating and viewing DjVu documents, along with a cross-platform viewer such as DjView. Commercial software and libraries historically existed from LizardTech and other vendors, contributing to broader adoption in libraries, publishers, and government archives.

Use cases and advantages. DjVu is widely used for digitizing large collections of scanned material due to its high compression ratio and good visual quality at high zoom levels. It is commonly found in digital libraries, academic repositories, and digitization workflows where efficient storage and fast loading of scanned pages are important.

Limitations and considerations. DjVu is less universally supported in consumer software compared with PDF, which can affect interoperability. Open-source viewers and libraries help mitigate this, but some environments may require dedicated tools to view or process DjVu files.