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Image Compression

IP.com Disclosure Number: IPCOM000076061D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Eiselen, ET: AUTHOR [+2]

Abstract

This is an improved coding technique which is particularly useful in a number of image compression algorithms. In particular, it applies to any run length coding scheme that provides for special codes outside the normal set of codes used to encode the run lengths.

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Image Compression

This is an improved coding technique which is particularly useful in a number of image compression algorithms. In particular, it applies to any run length coding scheme that provides for special codes outside the normal set of codes used to encode the run lengths.

Suppose that the set of special codes is called S0, S1, S2, . . . SN. It is assumed that the decompressor knows the length of a scan line. Instead of sending the code for the last run length in each scan line, the S0 code could be inserted. This particular code then tells the compressor to fill the remainder of the scan line, however long, with white.

It is desirable to defer the insertion of the S0 code, or its equivalent, at the end of each scan line. Thus, if the following scan line is all white, an S1 code is substituted for the S0 code; if the next two scan lines are all white, an S2 would be substituted for the S0; etc. This approach permits an extremely high- compression ratio to be achieved in large white areas.

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