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DjVu
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Computer file format
DjVuFilename extensions<br>.djvu, .djv<br>Internet media type<br>image/vnd.djvu, image/x-djvu<br>Magic numberAT&TDeveloped byAT&T Labs – ResearchInitial release1998; 28 years ago (1998)Latest releaseVersion 26[1]<br>April 2005; 21 years ago (2005-04)<br>Type of formatImage file formatsContained byInterchange File FormatOpen format?Yes<br>DjVu [a] is a computer file format designed primarily to store scanned documents, especially those containing a combination of text, line drawings, indexed color images, and photographs. It uses technologies such as image layer separation of text and background/images, progressive loading, arithmetic coding, and lossy compression for bitonal (monochrome) images. This allows high-quality, readable images to be stored in a minimum of space, so that they can be made available on the web.
DjVu has been promoted as providing smaller files than PDF for most scanned documents.[3] The DjVu developers report that color magazine pages compress to 40–70 kB, black-and-white technical papers compress to 15–40 kB, and ancient manuscripts compress to around 100 kB; a satisfactory JPEG image typically requires 500 kB.[4] Like PDF, DjVu can contain an OCR text layer, making it easy to perform copy and paste and text search operations.
History<br>[edit]
The DjVu technology was originally developed, from 1996 to 2001,[4] by Yann LeCun, Léon Bottou, Patrick Haffner, Paul G. Howard, Patrice Simard, and Yoshua Bengio at AT&T Labs in Red Bank, New Jersey.[5]
Prior to the standardization of PDF in 2008,[6][7] DjVu was considered superior because it is an open file format,[citation needed] in contrast to the proprietary nature of PDF at the time. The declared higher compression ratio (and thus smaller file size) and the claimed ease of converting large volumes of text into DjVu format were other arguments for DjVu's superiority over PDF in 2004. Independent technologist Brewster Kahle in a 2004 talk on IT Conversations discussed the benefits of allowing easier access to DjVu files.[8][9]
The DjVu library distributed as part of the open-source package DjVuLibre has become the reference implementation for the DjVu format. DjVuLibre has been maintained and updated by the original developers of DjVu since 2002.[10]
The DjVu file format specification has gone through a number of revisions, the most recent being from 2005.
Revision history
Version
Release date
Notes
Unsupported: 1–19[citation needed]
1996–1999
Developmental versions by AT&T labs preceding the sale of the format to LizardTech.
Unsupported: Version 20[1]
April 1999
DjVu version 3. DjVu changed from a single-page format to a multipage format.
Supported: Version 21[1]
September 1999
Indirect storage format replaced. The searchable text layer was added.
Supported: Version 22[1]
April 2001
Page orientation, color JB2
Unsupported: Version 23[1]
July 2002
CID chunk
Unsupported: Version 24[1]
February 2003
LTAnno chunk
Supported: Version 25[1]
May 2003
NAVM chunk. Support for DjVu bookmarks (outlines) was added. Changes made by Versions 23 and 24 were made obsolete.
Latest version: Version 26[1]
April 2005
Text/line annotations
Legend:<br>Unsupported<br>Supported<br>Latest version<br>Preview version<br>Future version
The primary usage of the DjVu format has been the electronic distribution of documents with a quality comparable to that of printed documents. As that niche is also the primary usage for PDF, it was inevitable that the two formats would become competitors. It should however be observed that the two formats approach the problem of delivering high resolution documents in very different ways: PDF primarily encodes graphics and text as vectorised data, whereas DjVu primarily encodes them as pixmap images. This means PDF places the burden of rendering the document on the reader, whereas DjVu places that burden on the creator.
During a number of years, significantly overlapping with the period when DjVu was being developed, there were no PDF viewers for free operating systems—a particular stumbling block was the rendering of vectorised fonts, which are essential for combining small file size with high resolution in PDF. Since displaying DjVu was a simpler problem for which free software was available, there were suggestions that the free software movement should employ DjVu instead of PDF for distributing documentation; rendering for creating DjVu is in principle not much different from rendering for a...