# How to let background image cover entire Beamer slide?

I successfully use the usebackgroundtemplate command to set a background image for a specific slide in Beamer as follows

\documentclass{beamer}
\mode<presentation> {
\usetheme{CambridgeUS}
}

\begin{document}

\usebackgroundtemplate{%
\includegraphics[width=\paperwidth,height=\paperheight]{example-image-a}}

\begin{frame}[t]
\frametitle{hello}
blahblah
\end{frame}

\end{document}


However, the image seems to have just covered the main body area, the background of the \frametitle is still white as before. How could I set this image as background for the entire slide? Or at least for the \frametitle as well (just for the slides I want, not for the entire presentation)? Or any better solutions?

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The background colour for the frame title in the CambridgeUS theme uses the beaver colour scheme and is set to

\setbeamercolor{frametitle}{bg=gray!10!white}


You can remove the entire background colour by adding

\setbeamercolor{frametitle}{bg={}}


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Thanks a lot. It works! After a few tries, I found I can use brackets {} to limit the \setbeamercolor and \usebackgroundtemplate commands effects only in a certain frames. For instance: { \usebackgroundtemplate... \setbeamercolor... \begin{frame}blahblah...\end{frame} }. –  Daniel Oct 3 '13 at 1:37
@Daniel: Yes, scoping using groups limit the effects of certain commands (unless they're declared globally). –  Werner Oct 3 '13 at 1:39

Your problem is caused by the theme CambridgeUS. This, in turn, uses

\usecolortheme{beaver}
\useoutertheme{infolines}


The first of these is responsible for the white title box, whereas the second is responsible for the red/gray header and footer. Both are drawn on top of your background image; it's not true that the image is not made big enough.

I suppose that the theme CambridgeUS is not compatible with a full-paper image. If you decide what exactly you want, you will have to tweak the theme (more precisely, to replace or tweak the the two subthemes above) to produce it. @Werner's answer shows you how to get rid of the white background color set by beaver.

I'm keeping the first answer I gave below (before the MWE was added), just to show that the accused command produces indeed the desired effect.

The image covers the entire area of the slide. Notice that the only real difference between this and your code is the \usetheme{CambridgeUS}.

\documentclass{beamer}
\begin{document}
\usebackgroundtemplate{%
\includegraphics[width=\paperwidth,height=\paperheight]{img}}
\begin{frame}
\frametitle{This}
\begin{itemize}
\item that,
\item the other,
\item and the next.
\end{itemize}
\end{frame}
\end{document}


The image file is a copy of GNOME-GNOMEWall_1600x1200.jpg obtained from here. The result is this:

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Thank you so much for your kind explanation! –  Daniel Oct 3 '13 at 1:32