Image coding technique

Details Image coding technique Image coding technique

1983-06-20

1986-03-25

Olms, Douglas W.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358260, 358261, H04N 712, H04N 140, H04N 1417, H04N 1419

Patent

active

045787042

ABSTRACT:
In a first embodiment, an image signal is segmented into bilevel and multilevel regions. The picture elements, or pels, representing the bilevel regions are center-thresholded and encoded using a two-dimensional CCITT coding scheme. The pels representing the multilevel regions are coded in a differential pulse code modulation (DPCM) coder. The resulting DPCM errors are coded by an intermediate coder which assigns the i.sup.th one of an ordered plurality of codewords to represent each pel whose value is the i.sup.th most-frequently-expected to occur, given the values of predetermined ones of the neighbor pels. The intermediate codeword values are assigned such that the intermediate coder output stream contains long bit runs. That output stream is then run- and variable-length coded in accordance with a one-dimensional CCITT bilevel image coding scheme. In a second embodiment, 3-bit DPCM words are coded by assigning a variable length codeword to represent each pel a a function of its expected frequency of occurrence given the neighbor pel values.

REFERENCES:
patent: 3813485 (1974-05-01), Arps
patent: 4121259 (1978-10-01), Preuss et al.
patent: 4325085 (1982-04-01), Gooch
patent: 4363036 (1982-12-01), Subramaniam
patent: 4420771 (1983-12-01), Pirsch
"Binary Image Compression", Image Transmission Techniques, R. B. Arps, 1979, pp. 219-276.
"Picture Coding: A Review", Proc. of IEEE, vol. 68, No. 3, A. N. Netravali, Mar. 1980, pp. 366-406.
"Ordering Techniques for Facsimile Coding: A Review", Proc. of IEEE, vol. 68, No. 7, A. N. Netravali and F. W. Mounts, Jul. 1980, pp. 796-807.

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