Beamer, transparent background colour

[Zarko Cucej]

Dear all,
I like to have in beamercolorbox transparent background colour. This I
try to achieve with naive solution:

\setbeamercolor{block body}{fg=black,bg={yellow!10,\opaqueness{.5}} }

but it is to naive an so it doesn't work. Do any one better idea how to
modified minimal (dummy) example below, that it will has a described
features?

regards, Zarko

p.s. I attach the background image example (a helicopter)

\documentclass{beamer}
%---------------------------------------------------------------%
\usepackage[slovene,english]{babel}
\usepackage[cp1250]{inputenc}\usepackage[T1]{fontenc}
\usepackage{graphics,tikz}
%---------------------------------------------------------------%
\defbeamertemplate{background}{image}[1][]{
\pgfdeclaremask[matte={1 1 1}]{background image}{#1}
\pgfdeclareimage[interpolate=true,
height=.8\textheight,
mask=background image]{background image}{#1}
\begin{pgfpicture}{0cm}{0cm}{\the\paperwidth}{-\the\paperheight}
\pgfputat{\pgfxy(6.4,-4.8)}
{\pgfbox[center,center]%
{\pgfuseimage{background image}}}
\end{pgfpicture}%
}
\setbeamertemplate{background}[image][slika3]
\setbeamercolor{block body}{fg=black,bg=yellow!10}

%---------------------------------------------------------------%
\begin{document}
%---------------------------------------------------------------%
\begin{frame}
\framesubtitle{Expertise with OPNET}
\framesubtitle{Test of back colour transparencies}
%------------------------------------------------------------ 9
\begin{beamercolorbox}[sep=0pt,wd=80mm]{block body}
\begin{itemize}
\item Modeliranje, simuliranje in vrednotenje TK omrežij
\item Merjenje in modeliranje telekomunikacijskega prometa
\item Ekspertni sistemi za optimiranje radijskih omrežij
\item Kakovost storitev v usmerjevalnih protokolih
\item Komunikacije v sprotnem času
\item Storitve s programskim paketom OPNET
\end{itemize}
\end{beamercolorbox}
\end{frame}
%---------------------------------------------------------------%
\end{document}

[Kjell Magne Fauske]

>  slika3.JPG
> 29KViewDownload

Hacking beamercolorbox so that it is transparent seems not to be
straightforward. Look in the Beamer file 'base\beamerbasecolor.sty' if
you are adventurous. A better approach is probably to create a custom
environment that wraps the content inside a TikZ node with transparent
fill. Here is one way to do it:

\newenvironment{transbox}{%
\begin{tikzpicture}
\node[text width=\textwidth,
fill=yellow!10, fill opacity=0.5,text opacity=1] \bgroup%
}{\egroup;\end{tikzpicture}}

You can now write:

\begin{transbox}
\begin{itemize}
...
\end{itemize}
\end{transbox}

Here is your modified example:

%%%%

\documentclass{beamer}
%---------------------------------------------------------------%
\usepackage[slovene,english]{babel}
\usepackage[cp1250]{inputenc}\usepackage[T1]{fontenc}
\usepackage{graphics,tikz}
%---------------------------------------------------------------%
\defbeamertemplate{background}{image}[1][]{

\pgfdeclareimage[interpolate=true,
height=.8\textheight]{background image}{#1}

\begin{pgfpicture}{0cm}{0cm}{\the\paperwidth}{-\the\paperheight}
\pgfputat{\pgfxy(6.4,-4.8)}
{\pgfbox[center,center]%
{\pgfuseimage{background image}}}
\end{pgfpicture}%
}
\setbeamertemplate{background}[image][slika3]
\setbeamercolor{block body}{fg=black,bg=yellow!10}

\newenvironment{transbox}{%
\begin{tikzpicture}
\node[text width=\textwidth,
fill=yellow!10, fill opacity=0.5,text opacity=1] \bgroup%
}{\egroup;\end{tikzpicture}}

%---------------------------------------------------------------%
\begin{document}
%---------------------------------------------------------------%
\begin{frame}
\framesubtitle{Expertise with OPNET}
\framesubtitle{Test of back colour transparencies}
%------------------------------------------------------------ 9

\begin{transbox}

\begin{itemize}
\item Modeliranje, simuliranje in vrednotenje TK omrežij
\item Merjenje in modeliranje telekomunikacijskega prometa
\item Ekspertni sistemi za optimiranje radijskih omrežij
\item Kakovost storitev v usmerjevalnih protokolih

\item Komunikacije v sprotnem c(asu

\item Storitve s programskim paketom OPNET
\end{itemize}

\end{transbox}

\end{frame}
%---------------------------------------------------------------%
\end{document}

%%%%

Note. Your code for setting a transparent background picture is much
complicated than necessary. Recent versions of PDFTeX supports PNG
with alpha channel. You can replace all that mask stuff with an
\includegraphics and include a transparent PNG directly.

Hope this helps!

Regards,
Kjell Magne Fauske

[Sebastian Szwarc]

Kjell could you explain a little this code:

\defbeamertemplate{background}{image}[1][]{
\pgfdeclareimage[interpolate=true,
height=.8\textheight]{background image}{#1}
\begin{pgfpicture}{0cm}{0cm}{\the\paperwidth}{-\the\paperheight}
\pgfputat{\pgfxy(6.4,-4.8)}
{\pgfbox[center,center]%
{\pgfuseimage{background image}}}
\end{pgfpicture}%
\setbeamertemplate{background}[image][slika3]

I dont see this intuitive...{image} is command or just name of the image?
and why to use:
\setbeamertemplate{background}[image][slika3] if earlier there is only
one paramter [1][]

[Kjell Magne Fauske]

Your question should be directed to Zarko, but here it goes:

Zarko has used the \defbeamertemplate command to override the
background template. The \defbeamertemplate is powerful and highly
configurable. What Zarko does in this case is to first assign a
predefined option called 'image' to the background template. The
element takes one parameter, no default value is specified:

\defbeamertemplate{template name}{predefined option}[#arguments]
[default value]{template contents}

So when he wants to use this template he uses:
\setbeamertemplate{template name}[predefined option][argument]

I don't know if this makes much sense. I recommend reading chapter
'16.3.2 Using Beamer’s Templates' in the Beamer manual carefully to
understand all the details. 'image' is in this case just a name used
to trigger a specific variant of the background template. Beamer
defines a few variants of the background template, like for instance
grid. You invoke it using:

\setbeamertemplate{background}[grid]

You can even give it a parameter:

\setbeamertemplate{background}[grid][step=1cm]

- Kjell Magne Fauske

[Kjell Magne Fauske]

On Sep 29, 8:22 pm, Kjell Magne Fauske <kjel...@gmail.com> wrote:

> Zarko has used the \defbeamertemplate command to override the
> background template. The \defbeamertemplate is powerful and highly
> configurable. What Zarko does in this case is to first assign a
> predefined option called 'image' to the background template. The
> element takes one parameter, no default value is specified:
>

Technically he has not overridden the background template. He has
added a new variant of the background template.

- Kjell Magne Fauske

[Zarko Cucej]

Kjell Magne Fauske wrote:
> On Sep 29, 12:25 pm, Zarko Cucej <zarko.cu...@gmail.com> wrote:
>> Dear all,
>> I like to have in beamercolorbox transparent background colour. This I
>> try to achieve with naive solution:
>>
>> \setbeamercolor{block body}{fg=black,bg={yellow!10,\opaqueness{.5}} }
>>
>> but it is to naive an so it doesn't work. Do any one better idea how to
>> modified minimal (dummy) example below, that it will has a described
>> features?
>>
>> regards, Zarko
>>

[...]

>
> Hacking beamercolorbox so that it is transparent seems not to be
> straightforward. Look in the Beamer file 'base\beamerbasecolor.sty' if
> you are adventurous. A better approach is probably to create a custom
> environment that wraps the content inside a TikZ node with transparent
> fill. Here is one way to do it:
>
> \newenvironment{transbox}{%
> \begin{tikzpicture}
> \node[text width=\textwidth,
> fill=yellow!10, fill opacity=0.5,text opacity=1] \bgroup%
> }{\egroup;\end{tikzpicture}}
>
>
> You can now write:
>
> \begin{transbox}
> \begin{itemize}
> ...
> \end{itemize}
> \end{transbox}
>
> Here is your modified example:
>
> %%%%

[....]

thank you very much. thhis perfectly work!

kind regards, Zarko