[Tex/LaTex] tikz spy with beamer overprint

beameroverlaystikz-pgf

In my presentation, I want to successively highlight different parts of my image using the TikZ spy library.
Due to size constraints, the actual highlight is outside of the included image.
Therefore, I use beamers overprint environment with onslide.
This works fine for \node, but I cannot get it to work for \spy.

Below is a minimal, not working, example. I described the problems in the comments.

\documentclass[12pt]{beamer}
\usepackage{tikz}
\usetikzlibrary{spy}
\begin{document}
\begin{frame}
\begin{overprint}
\begin{tikzpicture}[spy using outlines={circle, blue, magnification=6, connect spies}]
% bluemarble from http://en.wikipedia.org/wiki/File:Apollo17WorldReversed.jpg
\node<1-> (image) at (0,0) {\includegraphics[width=6cm]{bluemarble}};
% this one compiles, but image jumps around
% \only<2->{\spy [size=3cm] on (1,1) in node at (4, 4);}
% this one fails to compile with: ! Extra }, or forgotten \endgroup.
% \onslide<2->\spy [size=3cm] on (1,1) in node at (4, 4);
% this one fails to compile with:
% Runaway argument?
% ]<2-> [size=3cm] on (1,1) in node at (4, 4); \end {tikzpicture} \end \ETC.
% ! Paragraph ended before \tikz@lib@spy@parse@opta was complete.
\spy<2-> [size=3cm] on (1,1) in node at (4, 4);
% these compile, but 'spy' is on every slide
% \onslide<2->{\spy [size=3cm] on (1,1) in node at (4, 4);}
% \uncover<2->{\spy [size=3cm] on (1,1) in node at (4, 4);}
\end{tikzpicture}
\end{overprint}
\end{frame}
\end{document}

The beamer user guide, section 6.3.1., Making Commands and Environments Overlay Specification-Aware, but I'm not sure how to apply this \renewcommand<> thing to \spy to make it overlay-specification aware, since \spy does not look like an "ordinary" command as I would create with (re)newcommand.

How can I use \spy without my image "jumping around", e.g. with a (preferably automatically calculated) bounding box remaining constant for the different slides?

Best Answer

You could try making the node an overlay: \only<2->{\spy [size=3cm] on (1,1) in node[overlay] at (4, 4);} Then you don't need the overprint environment at all. An overlay node means it is not added to the bounding box.

Related Solutions

[Tex/LaTex] Latex-Beamer: overprint-environment wobbles

Not very elegant perhaps, but you could simply add some negative vspace before the align*.

\documentclass[xcolor=dvipsnames]{beamer}
\mode<presentation>
\usetheme{Boadilla}

\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsfonts,amsmath,amssymb,amsthm}

\DeclareMathOperator{\Var}{Var}
\DeclareMathOperator{\E}{\mathbb E} 

\title{Dummy-Titel}
\subtitle{Dummy-Untertitel}
\author{Autor}

\date{\today}


\begin{document}

\begin{frame}{Erwartungswert}
    \begin{itemize}
        \item $\E(X_{t+1} | X_t = i) = \sum_{j=0}^{2N} j \cdot P(X_{t+1}=j | X_t = i)$
        \item $X_{t+1}$ binomialverteilt mit Parametern $n=2N$ und $p=\frac{i}{2N}$:
        $\Rightarrow \E(X_{t+1} | X_t=i) = n \cdot p = i$
        \item Martingal-Eigenschaft: $\E(X_{t+1} | X_t) = X_t$
    \end{itemize}
        \begin{overprint}
            \onslide<1>
            \vspace{-.5cm}
            \begin{align*}
                \E(X_t) &= \E(\E(X_{t+1} | X_t)) = \sum_{i=0}^{2N} E(X_{t+1} | X_t = i) \cdot P(X_t = i) \\
                &= \sum_{i=0}^{2N} \left( \sum_{j=0}^{2N} j \cdot P(X_{t+1}=j | X_t = i) \right) \cdot P(X_t = i) \\
                &= \sum_{j=0}^{2N} j \cdot \left( \sum_{i=0}^{2N} \cdot P(X_{t+1}=j , X_t = i) \right) \\
                &= \sum_{j=0}^{2N} j \cdot P(X_{t+1}=j) = \E(X_{t+1})
            \end{align*}
            \onslide<2>
            \begin{equation*}
                \Rightarrow \E(X_0) = \E(X_1) = \E(X_2) = \ldots
            \end{equation*}
        \end{overprint}
\end{frame}
\end{document}

[Tex/LaTex] TikZ spy and Beamer uncover

Why \uncover<2-> and \visible<2-> do not work I don’t know, but here are two work-arounds:

Work-Around 1: `\alt` + `\pgfkeysalso`

There are two /.styles and one /.code, to help with beamer:

invisible/.style={opacity=0,text opacity=0}
This style is not very beamer special because it sets only every opacity (draw, fill, text) to zero, which means: It is there, but you cannot see it. It occupies the same space, much like \phantom.
alt/.code args={<#1>#2#3}{\alt<#1>{\pgfkeysalso{#2}}{\pgfkeysalso{#3}}}
This code handler uses two things:
1. The \alt<overlay>{arg1}{arg2} macro provided by beamer that executes arg1 when on overlay, otherwise arg2; and
2. \pgfkeysalso which adds TikZ keys to a path without changing it otherwise. This is similar to adding [some keys=values] to a path.
visible on/.style={alt={#1{}{invisible}}}
This style is rather a shortcut to alt. It does nothing to a path on <#1> but hides in otherwise.

If you want to use overlay specification with a ,, e.g. <2,4>, you have to enclose it in { }: visible on={<2,4>}. (For that same reason are the alt arguments enclosed in braces.)

Code

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{shadows,spy,shapes.symbols}
\tikzset{
    invisible/.style={opacity=0,text opacity=0},
    visible on/.style={alt={#1{}{invisible}}},
    alt/.code args={<#1>#2#3}{%
      \alt<#1>{\pgfkeysalso{#2}}{\pgfkeysalso{#3}} 
    },
}
\begin{document}

\begin{frame}
    Space
    \begin{center}
        \begin{tikzpicture}[spy scope={magnification=1.5, size=2cm},every spy in node/.style={remember picture,overlay,magnifying glass,circular drop shadow,fill=white,draw,ultra thick, cap=round}]
            \node[rectangle, draw, minimum width=1cm, minimum height=1cm] (N) {};
            \spy[visible on=<2->] on (N) in node;
        \end{tikzpicture}
    \end{center}
\end{frame}
\end{document}

Work-Around 2: `overlay`

The TikZ key overlay prevents the update of the bounding box. The content is simply overlayed on the page with no respect for everything.

This does work in this case …

Code

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{shadows,spy,shapes.symbols}
\begin{document}

\begin{frame}
  Space
  \begin{center}
    \begin{tikzpicture}[spy scope={magnification=1.5, size=2cm},every spy in node/.style={remember picture,overlay,magnifying glass,circular drop shadow,fill=white,draw,ultra thick, cap=round}]
      \node[rectangle, draw, minimum width=1cm, minimum height=1cm] (N) {};
      \only<2->{\spy[overlay] on (N) in node;}
    \end{tikzpicture}
  \end{center}
\end{frame}
\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Latex-Beamer: overprint-environment wobbles

[Tex/LaTex] TikZ spy and Beamer uncover

Work-Around 1: \alt + \pgfkeysalso

Code

Work-Around 2: overlay

Code

Related Question

Work-Around 1: `\alt` + `\pgfkeysalso`

Work-Around 2: `overlay`