How can I superimpose tikzpicture on a certain part of the page?

Question

I have a beamer slide, with some text and some graphics, and I want to superimpose a tikz picture on it. Is that possible?

Answer 1

Yes, you can do this using the remember picture and overlay options for tikzpicture; a little example:

\documentclass{beamer}
\usepackage{tikz}
\usetheme{Madrid}

\begin{document}

\begin{frame}{Title Text}
\centering

CTAN lion drawing\\ 
by Duane Bibby.

\includegraphics[width=5cm]{ctanlion}
\begin{tikzpicture}[remember picture,overlay]
\node[fill=red!20,opacity=0.5,minimum size=7cm,circle] at (current page.center) {};
\end{tikzpicture}

\end{frame}

\end{document}