This module implements the classical Wiener filter\index{filter!Wiener} 
(in its simplest version),
that aims to restore an image $in$ by an image $out$ that minimizes the energy
$$E(out) = \int (K \star out -in)^2 + lambda \int |\nabla(out)|^2.$$
\index{denoising!wiener}
\index{deblurring!wiener}
The solution is obtained in Fourier domain with
$$\widehat{out}(\xi) = \widehat{in}(\xi) \cdot
\frac{\hat K^*(\xi)}{|\hat K|^2(\xi) + lambda\cdot \pi^2|\xi^2|},$$
where $\xi$ is normalized into $[-\frac 12,\frac 12]^2$ and
$\hat K$ is the Fourier transform of $K$.
\index{Fourier Transform}
If $lambda=0$, then the convention $\widehat{out}(\xi)=0$ is chosen
when $\hat K(\xi)=0$ (weak inverse).

\medskip

The blur kernel $K$ can be 
\begin{itemize}
\item specified directly in Fourier domain as a Fimage
($\hat K = kernel$ with the \verb+-K+ option), 
\item specified radially in Fourier domain as a Fsignal (\verb+-R+ option), yielding
$$\hat K(\xi) = rad(|\xi|),$$
\item chosen Gaussian (\verb+-g+ option), yielding
$$\hat K(\xi) = e^{-2g^2\pi^2|\xi|^2},$$ 
\item or left to identity (default).
\end{itemize}

\medskip

The \verb+-w+ option is no longer valid, due to the convention change on
$lambda$ (the weight now applies to the regularization term and not any more
to the fidelity term). Compatibility with this previous option is ensured
by replacing \verb+-w+ $w$ by \verb+-W+ $lambda$ with $lambda=1/w$.
