This modules takes two input images $in$ and $mod$, and builds the
output image $out$ such that
$$\forall \xi, \quad
\widehat{out}(\xi) = |\widehat{mod}(\xi)|\cdot 
\frac{\widehat{in}(\xi)}{|\widehat{in}(\xi)|}$$
(with the obvious convention $0/0=0$).
Thus, $out$ is an image that keeps the phase information of the Fourier
transform of $in$, but inherits the modulus information from $mod$.
\index{Fourier Transform}
\index{texture}
