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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?

share|improve this question
    
Looks like I don't really get your point. If the image was to be transparent, what would you expect to see through the transparent areas? As you also don't give any MWE we can only guess, if the background color is different from white. Above that you give in your code a .jpg image, but jpg does not support transparency. –  Benedikt Bauer Sep 25 '12 at 13:14
    
All I wanted to do was to change the opacity, but I didn't know how to express it! Sorry for the inconvinience :( –  Thanos Sep 25 '12 at 13:34
3  
Don't worry. As long as you try to help us by answering additional questions we'll try to help you even if you missed something in your initial post that might have been unimportant from your point of view but turned out to be important to answer your question. –  Benedikt Bauer Sep 25 '12 at 16:12
    
You are so nice! Thank you very much for the understanding! –  Thanos Sep 26 '12 at 12:14

1 Answer 1

up vote 13 down vote accepted

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}

enter image description here

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

\pgfdeclareimage[height=\paperheight,width=\paperwidth]{myimage}{cern-logo.jpg}
\usebackgroundtemplate{\tikz\node[opacity=0.3] {\pgfuseimage{myimage}};}
share|improve this answer
    
It's working!!! Thank you very much for your time!!! –  Thanos Sep 25 '12 at 13:33
    
@Thanos You're welcome! –  Gonzalo Medina Sep 25 '12 at 13:34
    
Can you explain the reason why "semi-colon" separating the triple curly brace? –  Say OL Sep 2 '13 at 16:52
1  
@SayOL It's TikZ syntax; \node (and all other drawing TikZ commands) end with a semi-colon. –  Gonzalo Medina Sep 2 '13 at 17:20
1  
@SabreWolfy This is caused by the default padding of the node. Just replace \node[opacity=0.3] by \node[opacity=0.3,inner sep=0]. –  Michal Kaut Dec 3 '13 at 12:05

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