This module prepares an uniformly quantized image to be the input of the 
module \verb+amle+ which reconstructs
an image by interpolating the missing level lines from the ones kept
(see the main reference~\cite{caselles.morel.ea:axiomatic} 
and~\cite{aronsson:extension}\cite{cao:absolutely}\cite{froment:functional} for
related works).

The preparation consists of building an image with $0$ everywhere but
at pixel locations $(x,y)$ adjoining the remaining level lines (which are borders of level sets).
At these locations, the value of the pixels $\mbox{out}(x,y)$ is given by the 
value $\lambda$ of the nearest level line in $\mbox{in}(x,y)$.
Because of the quantization process, adjacent level lines are multiple
of $\mbox{delta}=\delta$ where $\delta$ corresponds the quantization step, 
and in the input image only the last level line of value $\mu >= \lambda$ is
recorded. The value $\lambda$ is therefore recovered using the following 
scheme:

if $\mbox{in}(x,y) > \mu$ then $\mbox{out}(x,y) = \mu + \delta$,
else  $\mbox{out}(x,y) = \mbox{in}(x,y)$.
