J'ai trouvé le code latex dans cette page facebook: https://www.facebook.com/profile.php?id=100083349580271

    

\documentclass[a4paper,11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{calc}
\addtolength{\oddsidemargin}{-.875in}
\addtolength{\evensidemargin}{-.875in}
\addtolength{\textwidth}{1.75in}

\addtolength{\topmargin}{-.875in}
\addtolength{\textheight}{1.75in}
\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\newcommand{\syBrisse}[6][\textwidth-\pgfkeysvalueof{/pgf/inner xsep}-1mm]{%
\begin{center}
\par\bigskip%
\begin{tikzpicture}
% Grand rectangle
\node[rounded corners, text width=#1, align=justify, inner sep=8pt,
outer sep=0] (one) {\medskip\parbox[t]{\textwidth}{%
\vspace*{22pt}\par#6}};
% Méthode (invisible)
\node[text=black,anchor=north west,align=center, minimum height=20pt,
inner xsep=5pt] (two) at (one.north west) {\hspace*{.5mm} #5};
% Remplissage bleu supérieur qui recouvre « Méthode »
\path[fill=#2,draw=#2]
($(one.north east)+(0ex,-4.5pt)$) [rounded corners=3pt] --
($(two.north east)+(+22pt,-4.5pt)$) --
($(two.south east)+(4pt,0pt)$) [sharp corners] --
(two.south west) [rounded corners] --
(one.north west) --
(one.north east) [sharp corners] -- cycle;
% Titre
\node[text=black,anchor=north east,align=center, minimum height=20pt,
text height=2ex,inner sep=8pt, inner ysep=3pt] (three)
at ($(one.north east)+(0,-3pt)$) {\#4};
% Méthode (visible)
\node[text=white,anchor=north west,align=center, minimum height=20pt,
inner sep=8pt,inner ysep=6.5pt] (for)
at($(one.north west)+(0,1.5pt)$) {\hspace*{0.8mm}#5};
% Cadre extérieur
\path[draw=#2,line width=0.8pt]
(one.south west) [rounded corners] --
(one.south east) [rounded corners] --
(one.north east) --
(one.north west) [rounded corners] -- cycle;
% Liseré sous le truc bleu
\foreach \x in {10,20,...,100}
\path[opacity=\x*0.01]
($(one.north east)+(-0.4pt,-6.5pt+\x/100)$) [rounded corners=3pt,draw=gray!\x] --
($(two.north east)+(23.3pt-\x/100,-6.5pt+\x/100)$) [rounded corners=3.5pt,draw=gray!\x] --
($(two.south east)+(5.3pt-\x/100,-1.9pt+\x/100)$) --
($(two.south west)+(0.4pt,-1.9pt+\x/100)$);
\path[draw=white,line width=1.1pt]
($(one.north east)+(-0.4pt,-5.2pt)$) [rounded corners=3pt] --
($(two.north east)+(+22.3pt,-5.2pt)$) [rounded corners=3.5pt] --
($(two.south east)+(+4.3pt,-0.6pt)$) --
($(two.south west)+(+0.4pt,-0.6pt)$);
% Dégradé formant l'essentiel du contenu de la boîte
\begin{pgfonlayer}{background}
\path[fill=#3!5]
(one.south west) [rounded corners] --
(one.south east) [rounded corners] --
(one.north east) --
(one.north west) [rounded corners] -- cycle;
\path[opacity=0.5, top color=#3!5,bottom color=#3,middle color=#3!30]
(one.south west) [rounded corners] --
(one.south east) [sharp corners] --
($(one.south east)+(0ex,0.8cm)$) --
($(one.south west)+(0ex,0.8cm)$) [rounded corners] -- cycle;
\end{pgfonlayer}
\end{tikzpicture}
\end{center}
}

\begin{document}

\syBrisse{blue}{blue}{\textbf{Produit d'un vecteur par un nombre reel}}{\textbf{Méthode}}{%
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.""Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.  Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
}

\syBrisse{red}{red}{\textbf{Produit d'un vecteur par un nombre reel}}{\textbf{Méthode}}{%
"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.""Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."
}

\syBrisse{orange}{orange}{\textbf{Produit d'un vecteur par un nombre reel}}{\textbf{Méthode}}{%
Essai
}

\syBrisse{violet}{violet}{\textbf{Produit d'un vecteur par un nombre reel}}{\textbf{Méthode}}{%
Essai
}

\syBrisse{cyan}{cyan}{\textbf{Titre}}{\textbf{Méthode}}{%
Essai
}

\end{document}