[Tex/LaTex] Transparent image background in beamer

Question

I want to add a background image in my beamer presentation. The thing is that when I use

\usebackgroundtemplate{
\includegraphics[width=\paperwidth,
height=\paperheight]{cern-logo.jpg}
}

in my preamble, the image has its true colors, meaning that it is not opaque or transparent. Is there a way to achieve that?

Answer 1

You can use TikZ to place the image in a \node with the desired opacity:

\documentclass{beamer}
\usepackage{tikz}

\usebackgroundtemplate{%
\tikz\node[opacity=0.3] {\includegraphics[height=\paperheight,width=\paperwidth]{ctanlion}};}

\begin{document}

\begin{frame}
CTAN lion drawing by Duane Bibby.
\end{frame}

\end{document}

In this case, it might be convenient to use \pgfdeclareimage, \pgfuseimge:

\pgfdeclareimage[height=\paperheight,width=\paperwidth]{myimage}{cern-logo.jpg}
\usebackgroundtemplate{\tikz\node[opacity=0.3] {\pgfuseimage{myimage}};}