%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Copyright 2010 Jasper Bosch <p.j.bosch@student.rug.nl>  %
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% Some parts of this theme are based on the 'diepentheme' %
% by Guido Diepen <diepen@cs.uu.nl>                       %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\RequirePackage{calc}
\RequirePackage{tikz}

% link to the backgroundimage, default is blackboard.png
% image should be in the same directory as the other files
\def\blackboard@backgroundimagefile{blackboard_bk.jpg}
\DeclareOptionBeamer{backgroundimagefile}{\def\blackboard@backgroundimagefile{#1}}
\ProcessOptionsBeamer

\mode<presentation>

\pgfdeclareimage[interpolate=true, height=\the\paperheight, width=\the\paperwidth]{backgroundImage}{\blackboard@backgroundimagefile}

% stretch background image over the entire page
\setbeamertemplate{background}{
	\begin{tikzpicture}
		\useasboundingbox (0,0) rectangle (\the\paperwidth, \the\paperheight); 
		\pgftext[at=\pgfpoint{0cm}{0cm}, left, base]{\pgfuseimage{backgroundImage}}; 
	\end{tikzpicture}
}

% use a small dash ('-') for a bulletpoint list
\setbeamertemplate{itemize items}{\usebeamercolor[fg]{item}\small{•}}
%\setbeamertemplate{itemize itemize item}{\usebeamercolor[fg]{item}\small{*-}}

\defbeamertemplate*{frametitle}{blackboard theme}[1][left]
{
  \begin{beamercolorbox}{frametitle}
  \vskip5pt  %17pt
  %\usebeamerfont{my frametitle}
  \insertframetitle \\
  \usebeamerfont{framesubtitle}\insertframesubtitle
  \end{beamercolorbox}
}