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From: spf@clyde.UUCP
Newsgroups: comp.graphics
Subject: Re: Thining out a bitmap image.
Message-ID: <11244@clyde.ATT.COM>
Date: Mon, 20-Jul-87 10:53:16 EDT
Article-I.D.: clyde.11244
Posted: Mon Jul 20 10:53:16 1987
Date-Received: Tue, 21-Jul-87 06:31:10 EDT
References: <275@uvicctr.UUCP>
Sender: nuucp@clyde.ATT.COM
Reply-To: spf@moss.UUCP (Steve Frysinger)
Organization: AT&T Bell Laboratories, Whippany NJ
Lines: 22

In article <275@uvicctr.UUCP> sbanner1@uvicctr.UUCP (S. John Banner) writes:
>
>    I have recently been called upon to write a program that takes
>a bitmap image, and converts it to a second bitmap image, such that
>no two points within a given radius of each other are left on.
>... an algorithm where you read in a bunch of lines, then scan through
>the image, point by point until you get to an on pixel, then blank
>out everything within the given radius, and continue on.
>... the program should not have to read in the entire bitmap (only a
>small fraction of the map will fit...)

The central problem with this approach is that you will get a
different result depending upon where in the image you start and in
which direction you traverse it.  I don't know what you intend to do with
the product, but I would think this is undesirable.  If you can get
enough of the image in memory to use a statistical, rather than
a "first-encountered" approach, your result would be invariant under
changes in starting point.  Essentially, you would calculate the central
pixel (suitably defined for your purposes) and then turn off any on pixels
in its neighborhood.

Steve Frysinger