Take the 2-minute tour ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

With Inkscape (software to create vector images) I created a file with several layers. Thanks to a very useful script (beamerscape), these layers are then saved as separate PDF files. Next, using overlay, the layers step-by-step appear as overlaying graphics in the presentation, like this:

\documentclass{beamer}

\usepackage[absolute,overlay]{textpos}
\textblockorigin{0mm}{0mm}

\begin{document}

\begin{frame}[t]{Some title...}
Some text...
\transdissolve<3,5,7>

% Layer "1<1-2,8>"
\pgfdeclareimage[width=\paperwidth]{Layer1}{Figures/Layer1}
\begin{textblock}{1}(0,0)
\pgfuseimage<1-2,8>{Layer1}
\end{textblock}

% Layer "2<2-4,8>"
\pgfdeclareimage[width=\paperwidth]{Layer2}{Figures/Layer2}
\begin{textblock}{1}(0,0)
\pgfuseimage<2-4,8>{Layer2}
\end{textblock}

% Layer "3<4-6,8>"
\pgfdeclareimage[width=\paperwidth]{Layer3}{Figures/Layer3}
\begin{textblock}{1}(0,0)
\pgfuseimage<4-6,8>{Layer3}
\end{textblock}

% Layer "4<6-7,8>"
\pgfdeclareimage[width=\paperwidth]{Layer4}{Figures/Layer4}
\begin{textblock}{1}(0,0)
\pgfuseimage<6-7,8>{Layer4}
\end{textblock}

\end{frame}

\end{document}

As you can see, the first layer only appears in steps 1 and 2 (the transdissolve effect isn't necessary of course). What I would like is that in step 2, so after step 1, this first layer is displayed in a lighter color (so a little transparent, like the \uncover command can do with for instance lists or equations).

Likewise, the second layer should appear in step 2 just as it is, and then in step 3 and 4 (or perhaps only step 4) fade to a lighter color.

As example for the graphics, imagine layer 1 as a full circle, and layer 2 as a part of this full circle. When layer 2 overlaps layer 1 (as would be the case in step 2 in this example), you won't notice the transition to step 2 because this "part of a circle" is just displayed on top of the complete circle.

It is, by the way, not a solution to display layer 1 just in step 1 (and then display only layer 2 in step 2) -- I really want to display the full circle, layer 1, in a lighter color in step 2, with layer 2 (part of the circle) on top of it.

share|improve this question
add comment

1 Answer

up vote 2 down vote accepted

You can obtain the effect you want as follows:

\documentclass{beamer}

\usepackage{tikz}

\usepackage[absolute,overlay]{textpos}
\textblockorigin{0mm}{0mm}

\begin{document}

\begin{frame}[t]

\pgfdeclareimage[interpolate=true,height=\textheight]{layer1}{circle}
\pgfdeclareimage[height=\textheight]{layer2}{square}

\begin{textblock}{1}(0,0)
  \begin{tikzpicture}
    \only<1>{\node[opacity=1]{\pgfuseimage{layer1}}};
    \only<2->{\node[opacity=0.5]{\pgfuseimage{layer1}}};
  \end{tikzpicture}
\end{textblock}

\begin{textblock}{1}(0,0)
  \begin{tikzpicture}
    \only<2>{\node[opacity=1]{\pgfuseimage{layer2}}};
    \only<3->{\node[opacity=0.5]{\pgfuseimage{layer2}}};
  \end{tikzpicture}
\end{textblock}

\end{frame}

\end{document}

This displays a circle in the first slide, and in the second a square in full opacity circumscribed in the circle which is 50% transparent.

share|improve this answer
1  
I think you can also use the colormixin environment, but I could not make the included image transparent, only some sample text. Maybe someone else knows how. –  Gustavo Aug 3 '12 at 16:20
    
Thanks, it's a perfect solution! In the end I decided to place all \only<...>{\node{...}} commands in just one textblock, because that way it looks a little more organized (I don't see why there should be four different textblock environments like in my original post -- I just used to code generated by the beamerscape script). –  Ailurus Aug 3 '12 at 18:26
    
Right, I thought I had a problem which made one image appear below (not behind) the other one, but I checked again and it works fine :) –  Gustavo Aug 3 '12 at 18:54
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.