djvu java
https://github.com/gthurm/javadjvu
https://www.programcreek.com/java-api-examples/index.php?api=com.lizardtech.djvu.Document
https://javadjvu.sourceforge.io/Deployment.html
http://forum.brighthand.com/threads/read-djvu-files-on-the-pocket-pc.216702/
http://javadjvu.foxtrottechnologies.net/0/8/08/doc/com/lizardtech/djvu/DjVuInterface.html
http://javadjvu.foxtrottechnologies.net/0/8/08/doc/allclasses-noframe.html
How to Convert Djvu File to PDF with Text Kept
http://shawnleezx.github.io/blog/2015/03/27/how-to-convert-djvu-file-to-pdf-with-text-kept/