[Tex/LaTex] How to add a transparent shadow to a block in beamer

beamershadowstransparency

Here my attempt to add a shadow to a block:

\documentclass{beamer}

% add a background image
\setbeamertemplate{background canvas}{\includegraphics[height=\paperheight]{example-image}}

% use rounded blocks with shadow
\setbeamertemplate{blocks}[rounded][shadow=true]

\begin{document}
\begin{frame}
  \frametitle{Block with shadow and with background image}

  \begin{block}{Block with shadow}
    Content...
  \end{block}
\end{frame}
\end{document}

The (poor) result:

enter image description here

The shadow hides my background!

Edit: beamer offered this feature for some time, but it is incompatible with the latex-dvips-ps2pdf route. I suppose this feature could be optional…

Best Answer

A possible first approach, redefining \beamerboxesrounded and \endbeamerboxesrounded (as defined in beamerbaseboxes.sty) to use a change of opacity through \pgfsetfillopacity; the lines of code that were included are marked with % NEW; the desired opacity can be changed using the \opacity command (initially set to 0.5):

\documentclass{beamer}
\usepackage{tikz}

\newcommand\opacity{0.5}

\makeatletter
\renewcommand\beamerboxesrounded[2][]{%
  \global\let\beamer@firstlineitemizeunskip=\relax%
  \vbox\bgroup%
  \setkeys{beamerboxes}{upper=block title,lower=block body,width=\textwidth,shadow=false}%
  \setkeys{beamerboxes}{#1}%
  {%
    \usebeamercolor{\bmb@lower}%
    \globalcolorstrue%
    \colorlet{lower.bg}{bg}%
  }%
  {%
    \usebeamercolor{\bmb@upper}%
    \globalcolorstrue%
    \colorlet{upper.bg}{bg}%
  }%
  %
  % Typeset head
  %
  \vskip4bp
  \setbox\bmb@box=\hbox{%
    \begin{minipage}[b]{\bmb@width}%
      \usebeamercolor[fg]{\bmb@upper}%
      #2%
    \end{minipage}}%
  \ifdim\wd\bmb@box=0pt%
    \setbox\bmb@box=\hbox{}%
    \ht\bmb@box=1.5pt%
    \bmb@prevheight=-4.5pt%
  \else%
    \wd\bmb@box=\bmb@width%
    \bmb@temp=\dp\bmb@box%
    \ifdim\bmb@temp<1.5pt%
      \bmb@temp=1.5pt%
    \fi%
    \setbox\bmb@box=\hbox{\raise\bmb@temp\hbox{\box\bmb@box}}%
    \dp\bmb@box=0pt%
    \bmb@prevheight=\ht\bmb@box%
  \fi%
  \bmb@temp=\bmb@width%
  \bmb@dima=\bmb@temp\advance\bmb@dima by2.2bp%
  \bmb@dimb=\bmb@temp\advance\bmb@dimb by4bp%
  \hbox{%
    \begin{pgfpicture}{0bp}{+-\ht\bmb@box}{0bp}{+-\ht\bmb@box}
      \ifdim\wd\bmb@box=0pt%
        \color{lower.bg}%
      \else%
        \color{upper.bg}%
      \fi%
      \pgfpathqmoveto{-4bp}{-1bp}
      \pgfpathqcurveto{-4bp}{1.2bp}{-2.2bp}{3bp}{0bp}{3bp}
      \pgfpathlineto{\pgfpoint{\bmb@temp}{3bp}}
      \pgfpathcurveto%
      {\pgfpoint{\bmb@dima}{3bp}}%
      {\pgfpoint{\bmb@dimb}{1.2bp}}%
      {\pgfpoint{\bmb@dimb}{-1bp}}%
      \bmb@dima=-\ht\bmb@box%
      \advance\bmb@dima by-2pt%
      \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
      \pgfpathlineto{\pgfpoint{-4bp}{\bmb@dima}}
      \pgfusepath{fill}
    \end{pgfpicture}%
    \copy\bmb@box%
  }%
  \nointerlineskip%
  \vskip-1pt%
  \ifdim\wd\bmb@box=0pt%
  \else%
  \hbox{%
    \begin{pgfpicture}{0pt}{0pt}{\bmb@width}{6pt}
      \bmb@dima=\bmb@width%
      \advance\bmb@dima by8bp%
      \pgfpathrectangle{\pgfpoint{-4bp}{-1bp}}{\pgfpoint{\bmb@dima}{8bp}}
      \pgfusepath{clip}
      {\pgftransformshift{\pgfpoint{-4bp}{0bp}}\pgftext[left,base]{\pgfuseshading{bmb@transition}}}%
    \end{pgfpicture}%
  }%
  \nointerlineskip%
  \vskip-0.5pt%
  \fi%
  \pgfsetfillopacity{\opacity}% NEW
  \ifbmb@shadow
    \setbox\bmb@boxshadow=\hbox{\pgfuseshading{bmb@shadow}}%
    \setbox\bmb@boxshadowball=\hbox{\pgfuseshading{bmb@shadowball}}%
    \setbox\bmb@boxshadowballlarge=\hbox{\pgfuseshading{bmb@shadowballlarge}}%
  \fi%
\setbox\bmb@colorbox=\hbox{{\pgfpicturetrue\pgfsetcolor{lower.bg}}}%
  \setbox\bmb@box=\hbox\bgroup\begin{minipage}[b]{\bmb@width}%
    \pgfsetfillopacity{1}% NEW
    \vskip2pt%
    \usebeamercolor[fg]{\bmb@lower}%
    \colorlet{beamerstructure}{upper.bg}%
    \colorlet{structure}{upper.bg}%
    %\color{.}%
  }

\def\endbeamerboxesrounded{%
  \end{minipage}\egroup%
  \wd\bmb@box=\bmb@width%
  \bmb@temp=\dp\bmb@box%
  \advance\bmb@temp by.5pt%
  \setbox\bmb@box=\hbox{\raise\bmb@temp\hbox{\box\bmb@box}}%
  \dp\bmb@box=0pt%
  \bmb@temp=\wd\bmb@box%
  \bmb@dima=\bmb@temp\advance\bmb@dima by2.2bp%
  \bmb@dimb=\bmb@temp\advance\bmb@dimb by4bp%
  \hbox{%
    \begin{pgfpicture}{0bp}{0bp}{0bp}{0bp}
      \ifbmb@shadow%
      {\pgftransformshift{\pgfpoint{4bp}{-3bp}}\pgftext{\copy\bmb@boxshadowball}}
      \begin{pgfscope}
        {%
\pgfsetfillopacity{1}% NEW
        \advance\bmb@temp by-1bp%
        \pgfpathrectangle{\pgfpoint{\bmb@temp}{-7bp}}{\pgfpoint{9bp}{9bp}}%
        \pgfusepath{clip}
        }%
        {\pgftransformshift{\pgfpoint{\bmb@temp}{1bp}}\pgftext{\box\bmb@boxshadowballlarge}}
      \end{pgfscope}
      \begin{pgfscope}
      \pgfsetfillopacity{\opacity}% NEW
        \advance\bmb@temp by-4bp%
        \pgfpathrectangle{\pgfpoint{4bp}{-7bp}}{\pgfpoint{\bmb@temp}{5bp}}
        \pgfusepath{clip}
        {\pgftransformshift{\pgfpoint{4bp}{-7bp}}\pgftext[left,base]{\copy\bmb@boxshadow}}%
      \end{pgfscope}
      \begin{pgfscope}
        \pgfsetfillopacity{\opacity}% NEW
        \advance\bmb@temp by 4bp%
        \bmb@dima=\ht\bmb@box%
        \advance\bmb@dima by\bmb@prevheight%
        \advance\bmb@dima by 4bp%
        \pgfpathrectangle{\pgfpoint{\bmb@temp}{1bp}}{\pgfpoint{4bp}{\bmb@dima}}
        \pgfusepath{clip}
        \advance\bmb@dima by-4bp%
        {\pgftransformshift{\pgfpoint{\bmb@temp}{\bmb@dima}}\pgftext{\box\bmb@boxshadowball}}
        \advance\bmb@dima by-1bp%
        \pgfpathrectangle{\pgfpoint{\bmb@temp}{1bp}}{\pgfpoint{4bp}{\bmb@dima}}
        \pgfusepath{clip}
        \advance\bmb@temp by4bp%
        {\pgftransformshift{\pgfpoint{\bmb@temp}{-3bp}}%
          \pgftransformrotate{90}%
          \pgftext[left,base]{\box\bmb@boxshadow}}%
      \end{pgfscope}
      \fi%
      \pgfsetfillopacity{1}% NEW
      \unhbox\bmb@colorbox%
      \pgfpathqmoveto{-4bp}{1bp}
      \pgfpathqcurveto{-4bp}{-1.2bp}{-2.2bp}{-3bp}{0bp}{-3bp}
      \pgfpathlineto{\pgfpoint{\the\bmb@temp}{-3bp}}
      \pgfpathcurveto%
      {\pgfpoint{\the\bmb@dima}{-3bp}}%
      {\pgfpoint{\the\bmb@dimb}{-1.2bp}}%
      {\pgfpoint{\the\bmb@dimb}{1bp}}%
      {
      \bmb@dima=\ht\bmb@box%
      \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
      \pgfpathlineto{\pgfpoint{-4bp}{\bmb@dima}}
      \pgfusepath{fill}
      }
      \ifbmb@shadow%
      {
        \color{black!50!bg}
        \pgfsetlinewidth{0pt}
        \pgfpathmoveto{\pgfpoint{\bmb@dimb}{-.5bp}}
        \bmb@dima=\ht\bmb@box%
        \advance\bmb@dima by\bmb@prevheight%
        \advance\bmb@dima by 1bp%
        \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
        \pgfusepath{stroke}
        \bmb@temp=\bmb@dima
        \advance\bmb@dima by 1bp%
        \color{black!31!bg}
        \pgfpathmoveto{\pgfpoint{\bmb@dimb}{\bmb@temp}}
        \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
        \pgfusepath{stroke}
        \advance\bmb@dima by 1bp%
        \advance\bmb@temp by 1bp%
        \color{black!19!bg}
        \pgfpathmoveto{\pgfpoint{\bmb@dimb}{\bmb@temp}}
        \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
        \pgfusepath{stroke}
        \advance\bmb@dima by 1bp%
        \advance\bmb@temp by 1bp%
        \color{black!6!bg}
        \pgfpathmoveto{\pgfpoint{\bmb@dimb}{\bmb@temp}}
        \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
        \pgfusepath{stroke}
        \advance\bmb@dima by 1.5bp%
        \advance\bmb@temp by 1bp%
        \color{bg}
        \pgfpathmoveto{\pgfpoint{\bmb@dimb}{\bmb@temp}}
        \pgfpathlineto{\pgfpoint{\bmb@dimb}{\bmb@dima}}
        \pgfusepath{stroke}
      }
      \fi
    \end{pgfpicture}%
    \box\bmb@box%
  }%
  \ifbmb@shadow%
    \vskip4bp minus 2bp%
  \else%
    \vskip2bp%
  \fi%
  \egroup% of \vbox\bgroup
}
\makeatother

% background image
\setbeamertemplate{background canvas}{%
  \tikz[remember picture,overlay]%
  \node at (current page) {\includegraphics[height=\paperheight]{example-image}};
}

% blocks with shadow
\setbeamertemplate{blocks}[rounded][shadow=true]

\begin{document}
\begin{frame}
  \frametitle{Block with shadow and with background image}

  \begin{block}{Block with shadow}
    Content...
  \end{block}
\end{frame}
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Beamerposter: rounded and shadowed blocks

I stumbled in a similar problem and solved it with the tcolorbox package. Here is the code:

\documentclass[final]{beamer}
\usepackage[orientation=portrait,size=a0,scale=1.4,debug]{beamerposter}     
\usepackage{tcolorbox}                                 %
\tcbuselibrary{skins}                                  %  preamble 
\usepackage{tikz}                                      %
\usetikzlibrary{shadows,shadings}                      %

\tikzset{myshadow/.style={                             % custom shadow with tikz
         opacity=.85,
         shadow xshift=0.15,
         shadow yshift=-0.15,
         shade,
         shading=axis,
         shading angle=230}
         } 
\tcbset{                                               % set a custom tcolorbox  
        skin=enhanced,                                 % enables use of shadows
        frame style={fill=gray,drop shadow={myshadow}}, % sets the frame color and the shadow properties
        bottom=7mm,                                    % distance between the body text and the bottom frame
        top=14mm,                                      % distance between the body text and the top frame
        boxrule=0mm,                                   % frame width
        bottomtitle=5mm,                               % distance between the title text and the bottom title frame               
        toptitle=5mm,                                  % distance between the title text and the top title frame
        lefttitle=1cm                                  % title text left margin
}  
\begin{document}
\begin{frame}  
\begin{columns}
\begin{column}{.3\textwidth}
\begin{tcolorbox}[title=\large Fontsizes]
 \centering
  {\tiny tiny}\par
  {\scriptsize scriptsize}\par
  {\footnotesize footnotesize}\par
  {\normalsize normalsize}\par
\end{tcolorbox}
\end{column}
\end{columns}
\end{frame}
\end{document}

the result is this:
enter image description here
for comparison:

I tried to explain everything in the code. If you want all the tcolorboxes to be like this, just put the \tcbset code in the preamble, otherwise start a group just before the tcolorboxes you want to customize in that way.

The only thing that doesn't really look the same is the shadow (my shadow isn't blurred), but with some tweaks and the shadows.blur tikzlibrary it should be possible to obtain the exact same result.

[Tex/LaTex] Permanent Transparent Block in a Frame in Beamer

Quoting the manual:

\invisible<⟨overlay specification⟩>{⟨text⟩}

This command is the opposite of \visible.

So, what does \visible do? Quoting again the manual:

\visible<⟨overlay specification⟩>{⟨text⟩}

This command does almost the same as \uncover. The only difference is that if the text is not shown, it is never shown in a transparent way, but rather it is not shown at all. Thus, for this command the transparency settings have no effect.

Therefore, if you really want to have the second block transparent, you don't have to use \invisible.

You can use \onslide for example, of course by specifying first \setbeamercovered{transparent}:

\documentclass{beamer}
\usepackage{lmodern}
\usepackage{mwe}% for dummy images
\usepackage{amsmath}
\usetheme{CambridgeUS}
\setbeamercovered{transparent}
\begin{document}
\begin{frame}
\only<1>{
\begin{block}{procedure-1}
 \centering% use this and not the center environment
 \includegraphics<1>[height=1.3in,width=4in]{example-image}
\end{block}
}
\only<2>{
\begin{block}{procedure-2}
 \centering% use this and not the center environment
 \includegraphics<2>[height=1.3in,width=4in]{example-image-a}
\end{block}
}
\only<3->{
\begin{block}{procedure-3}
 \centering% use this and not the center environment
 \includegraphics<3->[height=1.3in,width=4in]{example-image-c}
\end{block}
}
\onslide<4>{
\begin{block}{Mathematical Formulation}
\begin{equation}
 0+0=0
\end{equation}
\end{block}
}
\end{frame}
\end{document}

The result:

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Beamerposter: rounded and shadowed blocks

[Tex/LaTex] Permanent Transparent Block in a Frame in Beamer

Related Question