This module normalizes a shape using an affine-invariant process described
in~\cite{cohignac:reconnaissance}. 
Roughly speaking, this process applies an affine transformation on the
original shape $S$ in order the moments 
$$\mu_{pq}(S)=\int_{-\infty}^{\infty}\int_{-\infty}^{\infty}x^py^q \chi_S(x,y)dxdy$$
to satisfy some properties which cause this transformation to be unique. 
This way, we obtain an affine-invariant 
shape normalization which allows to compare and recognize shapes up to 
any linear transformation.
