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From: garye@hp-ptp.HP.COM (Gary_Ericson)
Newsgroups: comp.graphics
Subject: Cleaning up freehand drawings
Message-ID: <1580002@hp-ptp.HP.COM>
Date: 15 Sep 89 19:06:50 GMT
Organization: HP Pacific Technology Park - Sunnyvale, Ca.
Lines: 28

I was talking with someone once about a computer-based drawing system that 
would help the user draw by 'cleaning up' the things he/she draws.

What I mean is this.  Suppose I want to draw a straight line.  When I move the
digitizing pen (or mouse), I will undoubtedly not keep my hand steady and the
line will be crooked.  If the computer follows faithfully, I will end up with a
multi-segmented or curved line.  But what if the system decided that because
all the points I've digitized lie within a certain tolerance of a straight line
that I really wanted a straight line and it draws one for me.  I'm thinking of
maybe giving the pen a certain "thickness" (tolerance) and any points that lie
within that thickness of a straight line really represent a straight line.
Kind of like drawing with a fat felt-tip pen versus a fine pencil point.

It's a little harder for curves or splines, but I wonder if the same idea would
hold: if all the points, within the tolerance, lie along an arc or elipse or
spline of some kind, then the computer translates my sketch into that figure.

The idea is to smooth-out or straighten-out sketches input freehand.  Plus, if
the system knows it's generating a line or arc or whatever figure, it can treat
it as such a unit, rather than as a long series of individual points.

The question is: Has anyone developed algorithms (or, better yet, software) for
this kind of thing?  Is this possible or ridiculously difficult?

Disclaimer: I'm not a graphics expert of mathematician, just curious.

Gary Ericson - Hewlett-Packard
               phone: (408)746-5098  mailstop: 101N  email: gary@hpdsla9.hp.com