Why there is no pure java djvu encoders?

Question

If there is not any Java library that can encode djvu, what kind of potential difficulties may appear while trying to implement it?

Answer 1

The DjVu file format is open, but a full reference encoder is not part of the standard:

DjVu is an open standard. The file format specification, as well as an open source implementations of the decoder (and part of the encoder) are available.

This is due to patents:

Several patents apply to two very specific aspects of DjVu and DjVuLibre. The patents cover a particular aspect of the ZP-coder (the arithmetic coder used in DjVu and implemented in libdjvu/ZPCodec.cpp) and the background masking technique used in the IW44 wavelet encoder (implemented in libdjvu/IW44EncodeCodec.cpp).

There is an outdated GhostScript to DjVu converter, which may serve as a encoder reference.

References

• What is DjVu

• DjVu Licensing

• Java DjVu to PDF eBook converter

• JavaDjvu

• DjVuDocEditor Class Reference

• DidDjVu Project

• DjVuLibre Project

• Manual:How to use DjVu with MediaWiki