The DJVU file format, conceived in the mid-1990s by researchers at AT&T Labs, was designed to store scanned documents, especially those containing a combination of text, line drawings, and photographs. It is particularly well-suited for digitizing and compressing large volumes of paper-based content to be distributed over the internet due to its high compression ratio and the ability to preserve the quality of the original documents.
How DJVU Works
DJVU utilizes advanced compression techniques, including the separation of images into layers, such as a background layer for images and a foreground layer for text. This allows for high-quality images to be compressed more efficiently while maintaining the readability of the text. The format employs a technology called IW44 for the image layer, which is a wavelet-based method, and JB2 (equivalent to JBIG2) for compressing binary images for text. These technologies contribute to smaller file sizes compared to traditional formats like PDF.
Software Support for DJVU
A range of software supports the DJVU format. WinDjView and MacDjView are popular desktop viewers, while DjVuLibre provides an open-source platform for working with DJVU files. Additionally, various plugins and browser extensions are available for viewing DJVU files directly in web browsers. Document conversion programs often include the ability to convert from and to DJVU format, underlining its practicality in digital document management.
Alternatives to DJVU
Despite its advantages, the DJVU format is not as widespread as the Portable Document Format (PDF). PDF is more commonly used and is considered a universal standard for document exchange. Other alternatives include image formats like TIFF, known for its versatility in handling images and text but at the expense of larger file sizes. More recently, formats like EPUB for electronic books are gaining traction due to their reflowable and responsive design, making them preferable for mobile devices and e-readers.