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I found DjVu very useful as a format for saving scanned text, especially if together with a text layer processed with OCR so that text is searchable. For old books no more in commerce, that's often the only option available, albeit in a grey area.
I wonder however if the format is now dead for all practical purposes or not. Of course I can still use DjVu files for myself, and even compile source if necessary, but should I search for another format?
I have worked extensively with DjVu (and wrote the text extraction extension Calibre). I consider DjVu the better alternative for scanned multi-page documents, especially for efficiency reasons. Compared to the JPEG encoded pages you get in PDF or TIFF files you often have a 20x smaller file size.
For non-professional users this size difference often is not a problem, but for dessimination in the professional world it is. Just imagine having to buy 20x more storage and increased network capacity. Because a PDF reader is already necessary for many other documents (other than scanned), such users already have a PDF reader and I have seen a reluctance with non-professionals to install something just to be able to handle a more efficient file format.
DjVu is hindered by sub-par open source implementations of the encoder and AFAIK also by patent issues. My expectation is that at some point some replacement technology will become available that has all of the advantage and non of the problems, just like PNG replaced GIF. That will be a multilayer encoded image format.
As long as I will have some decent, commandline, conversion software for DjVu, PDF and any other format, I don't see any of that as a problematic. It would only be nice if I could tell Thunderbird which users only have a PDF reader so that I could attach DjVu and it would convert it to PDF before sending the email...
Good compression is only one of the advantages of the DjVu format, cf. e.g. my presentation.
I think however that we need better tools to handle the format conveniently. Some useful work has been already done by Jakub Wilk, cf. http://jwilk.net/software, but it is not yet enough.
In 2018 is no better format for eBooks with a complex text layout (magazines, encyclopedias). For pure text and minimal images is there epub format. I personally do not like PDF format. Badly working with this format.
There are not (good open source) tools to work with a PDF format, for example in Python.
Unfortunately, PDF is spread among ordinary people.
DjVu has python-djvulibre tools when development was supported by the Polish Ministry of Science and Higher Education grant no. N N519 384036 (2009-2012).
