Lossy compression is used when converting to DjVu format. This method is used to store scanned documents, which contain many formulas, symbols and pictures. All these signs and drawings are very difficult to fully recognize, and just the method of this compression is very convenient for such material.
What is DjVu Lossy Compression
Lossy compression method involves compressing the original document in such a way that the original data differs from those that will be obtained after unpacking the document. These changes are not so significant and with further use of the document compressed using this technology will not affect the final result.
The DjVu format is very convenient for compressing not only symbols and pictures. It is also often used when scanning any old documents and books. Here, not only the content of the original document is important, but also the color of the sheets, the texture of the paper, traces from bending sheets or from fingers, and the like. That is, when working with such source materials, every design nuance is important.
This document compression format is very popular and is often used when working with documents. Thanks to this technology, a number of libraries of scientific books have been created. To compress documents into DjVu format, a unique technology has been developed that allows you to divide the original image into three layers, which are called - foreground, background and black and white mask. The black and white mask contains the image of the text itself and all its clear details. All images and drawings are saved in the background, as well as the texture of the pages, the resolution of which is automatically reduced to save space. The information about the color contained in the mask is saved to the foreground. This layer shrinks even more. Then each of the layers is compressed using special algorithms.
How to convert to DjVu format?
As a rule, scanned documents are converted into DjVu format. Most often this is PDF format. To convert a document from PDF to DjVu format, you need special PDF to DJVU Converter software. It must be downloaded to your computer, most often the program is downloaded as an archive.
After downloading the archive, unpack it and then click on the installation file to install the program on your computer. When starting the program, you will need to specify in the Input File line the original PDF document that you plan to convert. Below, in the Output File column, indicate the folder into which the converted document will be saved already in the DjVu format. After these actions, click the "OK" button and the conversion process starts. It is recommended to open documents in DjVu format using Lizardtech Document Express Editor, which can not only open documents of this format, but also create them. In addition to these basic functions, it has a number of other advantages to help you work with DjVu documents.
In addition to working with old books and texts with complex symbols, this format is used by ordinary users to store a large amount of various literature on a computer, since when compressed, the document size is reduced to several megabytes.
