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From: lsr@apple.UUCP (Larry Rosenstein)
Newsgroups: net.micro.mac
Subject: Re: Calculating Region Areas
Message-ID: <43652@apple.UUCP>
Date: Tue, 9-Apr-85 12:37:03 EST
Article-I.D.: apple.43652
Posted: Tue Apr  9 12:37:03 1985
Date-Received: Thu, 11-Apr-85 23:58:40 EST
References: <ucbvax.6077>
Reply-To: lsr@apple.UUCP (Larry Rosenstein)
Distribution: net
Organization: Macintosh Division, Apple Computer
Lines: 20
Summary: 

A faster way to calculate the area of a region would be to create an
off-screen bitmap, do a FillRgn, and counting the 1 bits in the bitmap.
(Of course, you can optimize by checking for rectangular regions first.)

This requires only 1 regions operation, and you do not have to know the
region structure.  Counting the bits should be very fast, and could even be
done in assembler.  (My first thought would be to build a table that maps
the value of a byte into the number of 1 bits it contains, and iterate
through the bitmap a byte at a time.)

The only problem, is that you need to have enough memory for the off-screen
bitmap.


-- 
Larry Rosenstein
Apple Computer

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