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From: sjrapaport@watcgl.UUCP
Newsgroups: comp.graphics
Subject: Re: Intelligent scaling of bit-mapped graphics (Help!)
Message-ID: <379@watcgl.UUCP>
Date: Fri, 16-Jan-87 00:14:42 EST
Article-I.D.: watcgl.379
Posted: Fri Jan 16 00:14:42 1987
Date-Received: Fri, 16-Jan-87 07:29:28 EST
References: <2872@gitpyr.gatech.EDU> <2406@well.UUCP>
Reply-To: sjrapaport@watcgl.UUCP (Steve Rapaport)
Organization: U. of Waterloo, Ontario
Lines: 16

In article <2406@well.UUCP> ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) writes:
>In article <2872@gitpyr.gatech.EDU> dave@gitpyr.gatech.EDU (David Corbin) writes:
>>I am looking for information (programs, algorithms, references to texts)
>>on how to scale a bit-mapped image from one resolution to another, in an
>>intelligent manner....

A simple but expensive way:  map each new pixel onto the spot corresponding
to its centre on the old image.  Average the colors of all pixels that are
covered, weighting the average by area covered.  You now have a sloppy-looking
reproduction of your original image.  Most of the errors are high-frequency
noise, though, so you can clean it up a lot by running it through
a digital low-pass filter.  There it is.

I've never tried this myself, but it sounds feasible.  

-steve @ watcomputer