DjVu

Template: Infobox file format / Maintenance / Magic number is missing template: Infobox file format / Maintenance / default missing template: Infobox file format / Maintenance / missing site

DjVu [ deʒavy ] ( spoken language like deja vu, French " already seen " ) is an open file format for raster graphics, which is designed to store scanned documents and should represent an alternative to PDF.

Operation

The essential idea behind DjVu is the separation of the starting material in several layers and their different types of compression:

  • The page background and images contained are lossy compressed using a wavelet - based algorithm called IW44. This corresponds approximately to the JPEG 2000 compression.
  • The overlying text is compressed as a binary image with the so-called JB2 algorithm. This can work either lossless or lossy and does recurring patterns, such as letters, advantage.

In addition, text can directly, ie, not in the form of image data to be stored, which allows you to find and copy text passages. This text is generated in the case of scanned documents using OCR.

History

The underlying technology was developed from 1996 to the AT & T Laboratories and acquired in March 2000 by LizardTech. With the acquisition of LizardTech 2003 and its dissolution as an independent company in 2005, the property went to Celartem.

Software

From Celartem a reference implementation under the GNU General Public License ( GPL) was released, although a decoder, but contains only a partial encoder with which the severing of the background and text, as well as the lossy compression of text level is not possible in particular. The creation of DjVu files from scanned material is therefore currently only possible with commercial software or the DjVu Solo 3.1 software Celartem. The latter is available free of charge on the website.

To view DjVu files provides Celartem web browser plug-ins for Windows and Mac OS X at for free download. In addition, there DjVuLibre with a well-maintained by the original developers open source implementation with a viewer and browser plugin for Unix.

Free viewer on the basis of DjVuLibre library:

  • WinDjView & iTheater - viewer for Windows and Mac OS X
  • Evince - viewer for the GNOME desktop, even for other formats
  • Eyepiece, a universal document viewer (KDE)
  • STDU Viewer, a universal document viewer (Windows)
  • PocketDjVu - Viewer for Pocket PC
  • Sumatra PDF - viewer for Windows

DjVu files can be recovered using the free image viewer IrfanView open and extract, if you have installed the plug-in add-on package. From popular image editing software, the format is supported up to now neither write nor read.

Terms of Use

The algorithms used in the reference implementation and patented by Celartem can be used in the sense of the GPL open source projects continue, without fear of patent claims by Celartem.

Okular
242742
de