What is DJVU File Format
The .DJVU file extension refers to the DJVU file format. Originally developed at AT&T Labs in 1998, it is now available under a GNU General Public License. The latest specification is version 26 from 2005.
Despite being an open file format, several patents owned by AT&T apply to some specific aspect of this file type. In order to promote the development of the DJVU file format AT&T grants broad rights to users. The open-source version is called DJVULibre.
This file format was designed to contain scanned documents, and as an alternative to the PDF file format. The result has been a high performance file format, which is preferred and recommended by many experts. The main advantage of the DJVU file format is its capacity to store high quality, readable images in a minimum space. This allows for the image to be used on the web.
This efficiency is the result of the technologies included in the DJVU file format. They include image laser separation of text and background, progressive loading, arithmetic coding and lossy compression.
A DJVU file structure is based on the Interchange File Format, and is composed of several chunks, which are hierarchically organized. The different chunk types are used to describe the document, data shared by multiple pages, thumbnails, page dimensions, resolution and rotation.
The file compression is done by dividing an image into several images named background, foreground and mask; and using two compression technologies: a wavelet-based technique named IW44 and a compression algorithm called JB2. The foreground and background images are compressed via IW44, and the mask image is compressed using JB2. This last technology is still under AT&T license. Also under AT&T license is the ZP arithmetic coder.
DJVU viewers are available for the web browser, the desktop and the PDA devices. One of them is SumatraPDF for Windows. Other tools include the DJVU Reference Library released by Lizardtech under the GNU Public License version 2. This library can be freely extended by any interested party.
How to Open DJVU Files
What is the Digital Signature of a DJVU File
41 54 26 54 46 4F
52 4D nn nn nn nn
44 4A 56:
How to Recover Deleted DJVU Files
Losing a .DJVU file due to an unintended deletion is not uncommon in our present digital lives. Fortunately, Disk Drill, a data recovery app by Cleverfiles, can help you to recover DJVU files in a very easy and friendly way.
Disk Drill is based on some intelligent algorithms that search for content still available on the drive, and repair and reconstruct the .DJVU files. This is possible because when you deleted your .DJVU files, you actually only removed a reference to the data. The information remains on the drive, until overwritten by the operating system.
Disk Drill can work on a variety of digital devices, including internal and external hard drives, USB based drives, memory cards and more. In addition, it lets you perform your DJVU recovery on image files. These are bit-by-bit copies of an original digital device, which contain all data existing in the original source, including old deletions. They are used in Digital Forensics, as they allow for analysis of a device, keeping it unmodified.
Disk Drill is available for free!
Steps for Recovering DJVU Files Successfully
Once downloaded, the DJVU recovery procedure is easy. These are the few necessary steps:
- Install Disk Drill by clicking on the downloader’s icon. The program will guide you through the installation process with some easy to follow instructions.
- Open Disk Drill by clicking on the app’s icon. The app will detect all connected digital devices. In addition, you can attach image copies. Then, select the drive that contains your DJVU file(s).
- Narrow the scan by selecting the .DJVU file extension from the preferences menu. In this way, the search will be faster.
- Start the DJVU file recovery. This process can be cancelled or paused at any time. In addition, Disk Drill lets you save the session and continue later on, without any loss of the work already done. This is important when working with devices of a large size, as in these cases the process may take several hours.
- Once the search is completed, Disk Drill shows the results in the form of a list. This list can be narrowed down by using the available filters by date or size.
- Select the .DJVU file(s) that you need, and retrieve it (them) to a folder of your choice.
Your DJVU file recovery is done!