[lug] Off-topic: Contour line in image problem

[Glenn Murray]

Yes, the appeal of using something like the Gimp is that it might make
it easy to do manual manipulation of the image.  My question is the
one Ralf Mattes hinted at: once I get the embossed or mouse-drawn line
created, how do I get those pixels into a file of x,y coordinates?  At
that point I can think about getting the line's length.

I'm thinking it might be wiser to do the whole thing in some package
(e.g., Matlab), though I expect to lose the mousing.

But line integrals?  Laplace transforms?  The next time I teach Calc
III I'm going to make you guys sit in.

Glenn Murray
www.mines.edu/~gmurray/public_html/Welcome.html

On Thu, 6 Dec 2001, D. Stimits wrote:

> Rob Mohr wrote:
> > 
> > Approximate or match profile to a curve function.  Then integrate to calc
> > the area.  I would *guess* that cad programs such as AutoCad use a series
> > of Laplace Transforms to do the same thing.
> > 
> > Save for the challenge, and dusty math books, you can prolly get something
> > via a perl library and a good Google search string.
> > 
> > Rob Mohr (Iowa City, Iowa - Boulder, Colo )
> > eof
> > 
> > _______________________________________________
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> 
> Aha, that reminds me. If you have a drawing program that lets you draw
> curves, most likely Bezier, then it might be possible to simply bring in
> the bitmap (embossing would be an aid still), and manually draw a curve
> to the outline. Then it might be possible at some point to save with
> original Bezier specification in-tact. You'd then integrate along the
> curve. Possibly there are existing applications (like octave) that know
> how to directly find the line integral along the path of a Bezier (I
> haven't searched). In any case, it is probably easy to emboss via Gimp,
> and also easy to draw a curve free-hand, what you'd need to do is find a
> way to get free-hand drawings and pixmaps mixed on the same application.
> (and maybe scaling?)
> 
> D. Stimits, stimits at idcomm.com
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