The second test (\RefFig{fig:hard}) compares the performance of both
detectors on a quite difficult image with a lot of gradient noise. 
The new detector provides less outliers and misaligned segments, and
globally more relevant informations to infere the structure of the brick wall.
\begin{figure}[h]
%\center
  \begin{tabular}{
      c@{\hspace{0.1cm}}c@{\hspace{0.1cm}}c@{\hspace{0.1cm}}}
    \includegraphics[width=0.32\textwidth]{Fig_method/parpaings.png} &
    \includegraphics[width=0.32\textwidth]{Fig_hard/hardOld.png} &
    \includegraphics[width=0.32\textwidth]{Fig_hard/hardNew.png}
    \begin{picture}(1,1)
      {\color{dwhite}{
        \put(-286,4.5){\circle*{8}}
        \put(-171,4.5){\circle*{8}}
        \put(-58,4.5){\circle*{8}}
      }}
      \put(-288.5,2){a}
      \put(-173.5,2){b}
      \put(-60.5,2){c}
    \end{picture}
  \end{tabular}
  \caption{Evaluation on a quite textured image:
           1) imput image,
           2) results of the old detector,
           3) results of the new detector.}
  \label{fig:hard}
\end{figure}