Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!motcsd!lance
From: lance@motcsd.csd.mot.com (lance.norskog)
Newsgroups: comp.graphics
Subject: Re: Scaling Transformation on Bitmap Characters.
Message-ID: <2113@greek.csd.mot.com>
Date: 10 Nov 90 00:56:41 GMT
References: <1990Nov5.022837.15506@ucselx.sdsu.edu> <josef.658048934@peun11>
Organization: Motorola CSD, Cupertino CA
Lines: 27

I'd like to suggest another approach to scaling bitmaps.  I haven't
seen it mentioned anywhere but I'm sure someone smarter than me
thought it up first.

			Perceptron Scaling

This scheme only works for scaling in increments of small whole numbers.
In essence, you build a library of bit map pairs, and hunt for matches.
For example, if you are scaling up by 2, you have a complete set of input 
output pairs:

	* -	* * - -		* *	* * * *
	- -	* * - -		- -	* * * *
		- - - -			- - - -
		- - - -			- - - -

etc. to which you compare each incoming square of bits.  The imaginative
can come up with various fast searching algorithms.  To scale an image
four times up you can build a new 2->16 input/output set from the 2->4 set, 
but you might be better building a separate 16->64 set for better edge
and texture preservation.  (The preceding statement may be logically bogus).

Anyway, you get the idea.  The point is to preserve edges and textures via
searching for known input sets.  No, I haven't implemented it and have no
intention of doing so.

Lance Norskog