This module provides a very simple demo for how to use the Cimage memory
format in output.
It generates an image $256 \times 256$ with 256 gray levels, the column \#i having the gray level \#i.

Use the module cview to show it.

Note that an alternate form of this function could be
\begin{verbatim}
Cimage make_cimage()

{
  Cimage Output;

  ...

  return(Output);
}
\end{verbatim}
that is, to return the value using the function (and not passing an argument
to this function).
However, this alternate form is no longer recommanded since it allocates the
memory for the image at each call to the module (this can be wasting in case
of another module calling this one in a loop).

