Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!elroy!mahendo!jplgodo!wlbr!etn-rad!jru
From: jru@etn-rad.UUCP (John Unekis)
Newsgroups: comp.graphics
Subject: Re: Fractal Compression
Message-ID: <534@etn-rad.UUCP>
Date: 25 May 88 21:51:47 GMT
References: <686@thalia.rice.edu> <5546@cup.portal.com> <1947@tansei.cc.u-tokyo.JUNET> <522@etn-rad.UUCP> <1976@tansei.cc.u-tokyo.JUNET>
Reply-To: jru@etn-rad.UUCP (John Unekis)
Organization: Eaton Inc. IMSD, Westlake Village, CA
Lines: 33

In article <1976@tansei.cc.u-tokyo.JUNET> b39756@tansei.cc.u-tokyo.JUNET (Martin J. Duerst) writes:
>In article <522@etn-rad.UUCP> jru@etn-rad.UUCP (John Unekis) writes:
>>....
>>Suppose I give you an image from the real world. An example might be a 
>>digitized X-ray image. An exact representation of this image is absolutely 
>                           ^^^^^^^^^^^^^^^^^^^^
>    An exact representation of the original image is impossible, digitalization
>allways includes approximations. Instead of searching error-free compression
>algorithms, why not digitize at twice the resolution and use an approximate
>compression. 
..... I have been working in commercial applications for image processing for
over five years and I am painfully aware that all images are only approximate
representations of reality. What am I supposed to do, tell the hundreds of 
hospitals out there that have invested literally billions of dollars in medical
imaging equipment that they have to junk it all so that they can use my nifty
new image compression technique? Should I tell NASA that if they would only 
send up a whole new generation of satellites then my new compression technique 
would work out real well? Besides, if I digitize at twice the resolution I
am starting with 4 times the data, and I have to achieve 12 to 1 compression
to get to the same storage and I/O bandwidth requirements as a 3 to 1 
compression on a lower -resolution image.
     The key phrase above was *real world*, that is environments where things
like resolution, storage size, and I/O thruput are determined by existing
equipment.

>Even 10 to 1 is very good, 3 to 1 or four to 1 are more usual. If you have
>a good reference on an exact compression algorithm that acchieves 10 to 1,
>please mail me or post it.
>
 Sorry, the 10-to-1 compression was quoted by a San Francisco area start-up
 medical equipment manufacturer. The algorithm was proprietary, and they have
 since gone out of business. I saw some of the images at a trade show, and 
 although they looked good, the claim of truly non-destructive compression
 may not have been completely true.