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Re: QuickDraw InsetRgn algorithm

To: REALbasic NUG <realbasic-nug at lists dot realsoftware dot com>
Subject: Re: QuickDraw InsetRgn algorithm
From: Don Jungk <rb at flippingdades dot com>
Date: Fri, 31 Aug 2007 21:32:56 -0500
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References: <77124270708311617w6c578fa5gdd53735c4586eca4 at mail dot gmail dot com> <200708311844 dot 18808 dot rb at flippingdades dot com> <77124270708311729g1e733471sa8d96f63d4836c1 at mail dot gmail dot com>
On Friday 31 August 2007 7:29 pm, Peter K. Stys wrote:
> there's the rub Don: picking the "center" of a poly is key, else the
> poly will translate, and not just shrink.  The "centroid" (ie virtual
> center of gravity) is no good for concave polys (like a banana)
> because this point may lie outside the poly, so the poly will move.
>
> I really don't know how to do this correctly.  Seems so obvious!
>
Right, I can see a problem here. If we take a circle as an example, we know 
where the center is. Now, if we cut a small piece off of the circle it would 
change the calculated center, but we'd really like it to shrink the same as 
before using the same center point as before. I'm not sure that there is a 
mathematical answer to this.

If you find something that works, I hope you'll let us know.

Don
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