Symbol Dictionary Design for the JBIG2 Standard

The JBIG2 standard for lossy and lossless bi-level image coding is a very flexible encoding strategy based on pattern matching techniques. The encoder collects a set of symbols in a dictionary and encodes a page by reference to the dictionary symbols. JBIG2 allows the encoder to view all symbols and choose a good set for the dictionary. We propose a two-pass technique for choosing the dictionary entries, and discuss the trade-offs in bit allocation that these choices entail. The proposed dictionary design technique outperforms simpler dictionary formation techniques by up to 7-9% and 10-18% for lossless and lossy compression, respectively. In the lossy case, we further point out one way to significantly speed up the symbol bitmap compression procedure.