Browse Prior Art Database

Data Compressor

IP.com Disclosure Number: IPCOM000081246D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Cook, WC: AUTHOR

Abstract

A method is described for encoding a two-dimensional fixed image in a data image transmission system, so that the output digital code incorporates an indication as to the number of subsequent data words used to describe the run length encoded representation of all white or all black data blocks.

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Data Compressor

A method is described for encoding a two-dimensional fixed image in a data image transmission system, so that the output digital code incorporates an indication as to the number of subsequent data words used to describe the run length encoded representation of all white or all black data blocks.

The method comprises the steps of subdividing the image into a plurality of individual elemental areas to form a matrix, such as is shown in the pictorial data pattern storage 1 of fig. 1. A first two-by-two adjacent elements are allocated into a first data block, as shown. The first data block is scanned to determine whether it is all white or all black, by the switch 2 and the black/white discriminator 3. A first counter 4 is incremented if all the elements in the first block are white. A second counter 5 is incremented if all the elements in the first block are black. A next block is scanned to determine whether it is all white or all black and the appropriate counter 4 or 5 is incremented.

The scanning and incrementation is continued until a data block is scanned which does not contain either all white or all black elements. At this point, if a run of white blocks has been accumulated in counter the White run encoder 6 outputs a sequence of five-bit words as a run length encoder representation of the sequence of adjacent white data blocks. If a run of all black data blocks has been accumulated in counter 5, the black run encoder 7 outputs a sequence of five-bit data words as a run length encoder representation of the sequence of all the black data blocks.

The sequence of five-bit data words output by the encoders 6 and 7 commences with a first five-bit word, which...