RB to DJVU Converter

DjVu (pronounced "deja vu") is a document format developed at AT&T Labs by Yann LeCun, Leon Bottou, Patrick Haffner, and Paul Howard, first released in 1996. The format was specifically designed for storing scanned documents and images at very high compression ratios while maintaining visual quality suitable for on-screen reading. DjVu achieves this through a layered approach: the document image is separated into a foreground layer (text and line art at full resolution), a background layer (photographs and textures at reduced resolution), and a mask layer that determines which layer is visible at each pixel. This separation, combined with purpose-built compression algorithms for each layer type, typically produces files 5-10 times smaller than equivalent JPEG or PDF scans. One advantage is exceptional compression on scanned pages — a 300 DPI color scan that might occupy 25 MB as TIFF or 500 KB as JPEG typically compresses to 40-80 KB in DjVu while preserving legible text. The progressive rendering model is another strength: DjVu files stream efficiently over networks, displaying a readable low-resolution version almost immediately while progressively refining to full quality. The format supports multi-page documents, embedded text layers for searchability, hyperlinks, annotations, and a shared dictionary mechanism that further compresses collections of similar pages. DjVu is widely used by libraries and archives for digitized historical documents and manuscripts.