This modules shrinks a Fimage $in$ of size $M\times N$ into a Fimage $out$ 
of size $M'\times N'$, with 
$$1-\frac p{100}\leq \frac{M'}M \leq 1
\quad\mathrm{and}\quad
1-\frac p{100}\leq \frac{N'}N \leq 1
\eqno(1)$$ 
in order the complexity per pixel
of the Fast Fourier Transform (FFT)\index{Fourier Transform} of $out$
to be as small as possible. This amounts to minimize
$$C(M',N') = \sum_i (p_i-1) + \sum_j (q_j-1),$$
where $M'=\prod_i p_i$ and $N'=\prod_j q_j$ are the prime factor 
decompositions of $M'$ and $N'$, 
with the constraint (1). The new image $out$ starts at pixel
$((M-M')/2,(N-N')/2)$.
If the \verb+-v+ option is selected, the module writes on standart output
the initial and final complexity, and the speed-up ratio
$C(M,N)/C(M',N')$. 
\index{crop!an image}
