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From: Ilmari Karonen <iltzu@sci.invalid>
Newsgroups: alt.ascii-art
Subject: Re: Gwyneth Paltrow - Jave image->ascii conversion .. and discussion
 of  algorithms
Date: 20 Apr 2001 08:12:37 GMT
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 <3ADCB3E4.3404E133@rz.uni-karlsruhe.de>
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In article <3ADCB3E4.3404E133@rz.uni-karlsruhe.de>, Markus Gebhard wrote:
>
>Now if you go further and divide characters into more than 4 regions
>(e.g.3x2) it all becomes even worse and the results when I tried to do
>that were not worth considering.

Just as a data point, Rob Harley's classic bitmap-to-ascii algorithm
uses a 3x2 grid.  The details can be found near the end of Jorn Barger's
technical ascii art FAQ, archived for example at

  http://www.sci.fi/~iltzu/ascii/ada/aaatechnical.txt

FWIW, I did once write an algorithm that used a 5x5 (IIRC) grid of
grayscale values, doing least-square-sum analysis to pick the best
match.  It worked, in the sense that the output was recognizable, but it
was awfully slow and didn't look very good at all.

The major challenge in the field is IMHO developing a good non-local
asciification algorithm.  The problem, which also comes up in a way in
in ascflip, is that any algorithm that handles each character separately
is bound to yield suboptimal results in some cases due to aliasing.

-- 
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 ,_f_)\. Ilmari Karonen  iltzu@sci.fi  http://www.sci.fi/~iltzu/  /(_|_,.