This modules computes the inverse B-spline transform of a two-dimensionnal
array of numbers (Fimage). A mirror extension is used at the boundaries of
the array.
The coefficients $out(k,l)$ are computed in order to ensure that 
the B-spline interpolation
$$u(x,y) = \sum_{k,l} out(k,l) \;\beta^n(x-k) \, \beta^n(y-l)$$
satisfies $u(k,l)=in(k,l)$.
The spline $\beta^n$ is defined in the documentation of \verb+fcrop+ module.
The order of the spline $n$ ($order$) must be between $2$ and $11$.
The module is based on a recursive implementation of the associated $z$-filter
(see~\cite{thevenaz.blu.ea:image}\cite{unser.aldroubi.ea:fast})\index{filter!z-filter}.
\index{B-spline}
