Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!pmafire!mica.inel.gov!sapphire!highley
From: highley@sapphire.idbsu.edu (Larry Highley)
Newsgroups: comp.lang.pascal
Subject: R:Dewdney Algorithm for Cat Scanners
Summary: Need Help in Deciphering it
Message-ID: <1991Mar22.185337.23539@sapphire.idbsu.edu>
Date: 22 Mar 91 18:53:37 GMT
References: <1991Mar20.150624.27636@javelin.es.com> <1991Mar21.101704.8161@uwasa.fi>
Organization: Boise State University, Boise
Lines: 32


In Scientific American (September 1990) there is an article by A.K. Dewdney
on Mathematical Recreations.  It involves the use of Digital X rays or 
D rays as he calls them.  He goes on to give an algorithm for writing a 
program which is capable of scanning simple images from a set of 
D--rays which are both horizontal and vertical.  He also mentions Diagonal
D-rays.  I was wondering if anyone had actually written the program
and if so if I could have a look at it.  I would also be interested in
any help people can give since I'm relatively new to this.  Here is the   
algorith he provides.

	input x-array and y-array
	input xcount and ycount
	repeat
		done<--0
		for each array position I
		if x-array(I)=ycount and done=0
		then x-array(I)<--0
			for each y-array(J)>0
				decrement y-array(J)
				color square at (I,J)
			done<--1
		if y-array(I)<--0
			for each x-array(J)>0
			 	decrement x-array(J)
				color square at (J,I)
			done<--1
		compute new xcount and ycount
	until count =0

I could use any help possible.
Thanks!!:)