DjVuPlus
DjVu Read Documents,With OCR Technology(Arabic ,English ),Small Size
...) and the background masking technique used in the IW44 wavelet encoder (implemented in libdjvu/IW44EncodeCodec.cpp).
Most patents are owned by AT&T. LizardTech has very broad rights to them and grants free and permanent licenses to them for the purpose of building GPL software with the DjVu Reference Library. The grant is materialized by two paragraphs in the headers of the DjVu Reference Library source files. Lizardtech also published an official statement about the open source.