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From: ken@turtlevax.UUCP (Ken Turkowski)
Newsgroups: net.graphics
Subject: Re: Request for info on RUN-LENGTH CODE technique
Message-ID: <603@turtlevax.UUCP>
Date: Sun, 2-Dec-84 13:32:11 EST
Article-I.D.: turtleva.603
Posted: Sun Dec  2 13:32:11 1984
Date-Received: Tue, 4-Dec-84 08:14:26 EST
References: <4681@ukc.UUCP>
Reply-To: ken@turtlevax.UUCP (Ken Turkowski)
Distribution: net
Organization: CADLINC, Inc. @ Menlo Park, CA
Lines: 22
Keywords: runlength coding, sparse vector coding

Depending on the complexity of image, runlength coding produces worse
compression than a straight byte storage.  A mixture of the two is
helpful:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| run length  |     color     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+
|1|vector length|     color0    |   color1      | ... |  color n-1    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+

I have called this a "sparse vector" type of representation.  The runs
are of length 128 (instead of 256) max, because the most significant
byte is used to switch between runs and vectors.

Depending on the measure used, the break-even point is a run of 3, 4,
or 5.
-- 
Ken Turkowski @ CADLINC, Menlo Park, CA
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