[SciPy-dev] Fitpack, insert, and spline -> bezier conversion

Robert Kern robert.kern@gmail....
Tue Feb 6 21:06:46 CST 2007

Zachary Pincus wrote:
> Hello all,
> I've been working with scipy.interpolate a lot lately (hence some of  
> the noise on this list; sorry) to write some code to convert cubic  
> parametric b-splines into bezier curves (for easy output to things  
> like postscript or SVG).
> With the FITPACK 'insert' routine wrapped, this is relatively easy  
> once you figure out how, although there are a few gotchas. (Would  
> such a bit of code be useful in the scipy fitpack library?)

Yes, please!

> In the course of writing these conversion functions, I came upon some  
> subtle bugs in the original implementation of insert.f from netlib.  
> (They have to do with how the range into which the knot will be  
> inserted is chosen in corner cases that occur when converting  
> periodic splines to bezier curves.) I've tried contacting Dr.  
> Dierckx, but so far without luck.
> What would be the best approach to making sure that at least scipy  
> gets correct versions? Should I contact the netlib people?

They're probably not in a position to accept updates from anyone but the authors
themselves, but you can try.

> Should I  
> send you guys my patch and further fork the codebase?

That seems like the best thing to do.

Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco

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