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From: cs001005@cslab9c.cs.brown.edu (Thomas Colthurst)
Newsgroups: alt.fractals,comp.graphics
Subject: Re: How well does Barnsley's system perform?
Message-ID: <36191@brunix.UUCP>
Date: 12 Apr 90 20:06:15 GMT
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Reply-To: cs001005@cslab9c.cs.brown.edu (Thomas Colthurst)
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In <22023@bellcore.bellcore.com>, sjs@roland.ctt.bellcore.com (Stan
Switzer) writes:
>Regarding Barnsley's method:
>
>> I've seen one of the images which was compressed 10,000 to one.  It
>> took a huge amount of time ( I vaguely recall days) to do the
>> compression. Overall quality was not very good but what do you expect
>> at that compression rate?
>
>Unless the nature of the image degradation can be characterized in
>some formal way, the technique will only be useful for producing
>Gaughinesque renditions of scanned images.  I can see some
>applications where all you need is gee-whiz graphics, but I can't see
>how how it could be useful beyond that.
>
>On the other hand, if the nature of the image quality degradation
>could be formally (and publicly) described, then the technique might
>be useful in a wide range of applications.  As it stands, it is
>impossible to tell.

	It's hard to tell how well Barnsley's algorithm preserves quality
because we don't have the original pictures, just the reconstructed
images.  From my inspection, though, these don't look too bad.
	The nature of the image quality degradation is formally described by
the collage theorem, but this is only a theoretical result about the
potential of an IFS compression system, specifically that increase in
image detail can be obtained by only a linear increase in size of the
compression.  A specific algorithm that uses IFS compression may not
achieve that potential, or may acheive that potential only in n^3 time
or worse ...
	The evolutionary IFS compression algorithm that I am currently working
on will be able to achieve an arbitrarily specified level of detail, but
I haven't done a time analysis yet ...

-Thomas C