# How can one put labels over an image?

This question is slightly different from Drawing on an image with TikZ.

What I'm asking is how can I put a vertex label, at a particular point (x,y), on an image of a graph in TikZ?

\begin{center}
\begin{tikzpicture}
\node[anchor=south west,inner sep=0 <--What is this?] at (0,0) {\includegraphics[scale=.5]{graph.png}};
\node[???]{$v_1$};
\end{tikzpicture}
\end{center}

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I assume you mean Drawing on an image with TikZ‌​? The approach there can be used to place arbitrary objects on an image, not only for red rectangles on mushrooms. –  Jake Aug 2 '13 at 19:56
Yes, but I don't know how to draw a label. –  Trancot Aug 2 '13 at 19:57
Is it just a node? –  Trancot Aug 2 '13 at 19:58
I think I figured it out: \node[shift={(1.0,0.3)}]{$v_1$}; –  Trancot Aug 2 '13 at 20:09

You can place anything using this approach, not just rectangles.

To place text, you have to use \node at (<coordinates>) {<text>};:

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=0.9\textwidth]{mushrooms.jpg}};
\begin{scope}[
x={(image.south east)},
y={(image.north west)}
]
\node [white, font=\bfseries] at (0.25,0.65) {$P(X|Y)$};
\end{scope}
\end{tikzpicture}
\end{document}


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