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Data Compression for Raster Display

IP.com Disclosure Number: IPCOM000079701D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 44K

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. The method incorporates two modes of operation the first being runlength encoding of successive blocks of n by m elements which are either all black or all white, and the second mode being the reading out of each element in an n by m block of elements which is not either all black or all white.

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Data Compression for Raster Display

A method is described for encoding a two-dimensional fixed image in a data image transmission system. The method incorporates two modes of operation the first being runlength encoding of successive blocks of n by m elements which are either all black or all white, and the second mode being the reading out of each element in an n by m block of elements which is not either all black or all white.

Fig. 1a shows a portion of a DTV raster which is for this example, subdivided into a sequence of data blocks 1, 2, and 3, etc., each containing a 3 x 3 array of data elements. Fig. 1a shows a sequence of three successive all white data blocks. The method described encodes this sequence of data blocks by the runlength encoded word shown in Fig. 1b. Each runlength encoded word consists of five binary bit locations, the first two bits being the flag bits.

The first position flag bit is always a 1 if the code represents a runlength encoded sequence. The second position flag bit is a 0 if the data blocks to be encoded are all white, and is a 1 if the data blocks to be encoded are all black. The 3rd, 4th and 5th positions of the code word correspond to the delta field which can have a value from 0 to 7, indicating the number of successive all white or a data blocks which have been runlength encoded.

Fig. 2a shows a sequence of three successive all black data blocks, and Fig. 2b shows the corresponding code word for its runlength encoded repres...