The Djvu Format
The DjVu format was developed as an alternative to the PDF format. It is optimized for scanned documents which contain both pictures and text and in many cases performs better than PDF for this kind of documents considering the file size. Therefore it is frequently used for the distribution of scanned documents on the web. In contrast to PDF it is an open file format which means that it can be used by both open source software and proprietary software without any charge.
The DjVu format uses advanced compression technologies which are about 5 to 10 times better then those of JPEG and Tiff. A scanned page in color (resolution 300 DPI) with a file size of lets say about 25 MB can be easily compressed to only 100 kB (!) using DjVu. All DjVu documents can be equipped with a text-layer to make them searchable. These searchable DjVu documents behave very similar to PDF documents.
Differences between the DjVu and PDF Formats
>When it comes to sharing documents on the internet, the PDF file format is one of the most popular formats in use. If you are looking for an instruction manual online, there will probably be a PDF version of it. Many press releases, reports, and similar texts are also released in PDF form. That said; there are alternatives to the PDF, one of which is the DjVu file format. There are many similarities between the two actually though DjVu is less well known by many. While they do have characteristics in common, it is also important to consider those areas where one is better than the other.
One of the key advantages of the DjVu format is simply that it is more effective when it comes to compressing its documents. The idea here is that if you are going to take an existing scanned document, and you save it as both a DjVu file and a PDF file, the DjVu file is going to be significantly smaller than the PDF. Even if the compression is greater with DjVu, this does not mean tat the resulting document will look inferior to a PDF version. Instead, you end up with comparable looking documents of different sizes.
The smaller size of DjVu files is important because it will affect the experience of viewing these files online and downloading them onto computers, tablets, and mobile phones. It is important to keep in mind that people have varying access to bandwidth. Some people will have high-speed internet so large file sizes will not be an issue for them. However, many people have less than stellar internet speeds so they would benefit from file sizes that are significantly smaller. In real world use, a DjVu file online will tend to load quicker than a similar PDF.
Speed is one important benefit because people do not want to waste time waiting for a document to load. In this case, DjVu is better than PDF. Size is also important because there are many people whose internet access comes with data caps. If they go over the allotted amount of data, their internet speeds usually drop considerably. So if the documents they need are smaller in size, it will take longer for them to hit their data caps.
While the DjVu file format has the advantage in terms of size and speed, the PDF file format has the benefit of greater familiarity. If a person receives a PDF file in an email, she will usually have a program on her computer or tablet that can be used to open it. However, a DjVu file may have some people scratching their heads, wondering what it is. So this is one area where the DjVu format still has some way to go.