Specifications

COPYRIGHT © 1999 CANON INC. CANON SUPER G3 FAX BOARD-F1 REV.0 MAY 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
2-39
CHAPTER 2 OPERATION AND TIMING
C. JBIG Image Compression Coding Method
1. Outline of the JBIG Image Compression Coding Method
The JBIG image compression coding method is a new way of coding binary image data (black
and white) developed by the Joint Bi-Level Image Experts Group, and its rules are standardized as
part of ITU-T T.82/5.85.
The JBIG image compression coding method provides a higher rate of compression than the
existing MMR coding method (1.1 to 30 times as high) when handling text, pseudo halftone with
limited black-and-white continuity, and halftone processed by a dither method. It can also be
characterized by the fact that the size of coding after compression will not exceed the initial size of
data and by its ability to reproduce original images progressing during decoding as in the case of the
existing MR/MMR method (i.e., fully reversible).
The JBIG image compression coding method is either of two types: progressive bi-level image
compression designed for image data base searches (standardized in ITU-T T.82) and single
progressive sequential bi-level image compression designed for fax communication (standardized in
ITU-T T.82 and T.85). Figure 2-401 shows conceptual diagrams of these two methods.
Figure 2-401 Conceptual Diagrams
Progressive transmission
Sequential transmission