Changing margin for a part of page only

I would like to change the margin for an image only, I've used

\newgeometry{left=0.5cm,bottom=0.1cm,right=0.5cm}
\restoregeometry


But it affects an entire page

for local extension of text width for one equation or image you can use changepage package and his macro adjustwidth:

% preamble ...
\usepackage[sctrict]{changepage}
% ...

\begin{figure}
\includegraphics[width=\linewidth]{Organigramme.png}
\end{figure}
% ...


Thank's to comment I got it to work using minipage and negative \hspace

  \begin{figure}\centering
\begin{minipage}[c]{\textwidth}
\hspace{-2.85cm}
\includegraphics[scale=0.55]{Organigramme.png}
\end{minipage}
\end{figure}

• Don't put a figure environment inside a center environment like that, the figure could easily float away, and then you're left with some unwanted vertical space generated by the center environment. To center the contents of a figure environment add \centering right after \begin{figure}. – Torbjørn T. Aug 24 '16 at 7:54
• The minipage is not needed; just use \hspace*{<dim>}% – egreg Aug 24 '16 at 19:56