[MfA]

Originally Posted by mikenadia

Am I right in thinking that the difference between the b-spline (infinite support) and the Panorama method (finite support) is "those boundary conditions".

Not really. Also poor performance of b-spline at the edges is probably partly caused by the choice of edge extension (mirroring doesn't work well on gradients for obvious reasons, doing say 8 pixels of point symmetric edge extension before doing the normal interpolation would probably help).

MfA, if it makes sense to implement it , can you help to understand the Unser algo for a "true" spline interpolation? Is it this one? (p 7) bigwww.epfl.ch/publications/thevenaz0002.pdf

Yes, that's the one ... they also have an implementation :
http://bigwww.epfl.ch/thevenaz/interpolation/

As for the math, meh ... too much work, I understand the implementation though They use 2 IIR filters, one right to left and one left to right ... after that you can use the resulting coefficients in plain b-spline interpolation.

May be , I will get more luck with http://www.cs.sunysb.edu/~mueller/pa...s98_Design.pdf
In Appendix, coefficients with the optimal interpolation that is C2 and 4EF (6 filter weights).

Doubt it, but who knows.