TikZ externalize, pgfplots and animate

Question

I gave a very fetching presentation written with beamer today. It included a pgfplot animated with the animate package, and the result was fantastic. The problem? One of my colleagues wants to borrow the plot for a presentation written in something non-LaTeX. In addition, it would be nice to know how to externalise animated pgfplots frame by frame for animation using using convert or mencoder to produce a standalone file for inclusion in websites etc.

Naturally, I turned to externalize to do the job for me. It seems that animate and externalize don't agree... How can I convince them to kiss and make up?

Below is a massively simplified example for the wizards to work with

\documentclass{standalone}
\usepackage{pgfplots}
\usepackage{animate}
% Comment out the following line to see what the plot looks like.
\usepgfplotslibrary{external}\tikzexternalize 

\begin{document}
%
\begin{animateinline}[controls]{10}
  \multiframe{30}{ind=0+1}{
    \begin{tikzpicture}
      \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
        \addplot {sin(deg(x+\ind*pi/16))};
      \end{axis}
    \end{tikzpicture}
  }
\end{animateinline}
%
\end{document}

Answer 1

Does the animate package do things with the shipout routine of TeX? The external lib replaces it -- probably in an incompatible way.

Nevertheless, the following approach also works:

\documentclass{article}
\usepackage{pgfplots}
\usepackage{animate}
% Comment out the following line to see what the plot looks like.
\usepgfplotslibrary{external}

\tikzexternalize


\begin{document}
%
\begin{animateinline}[controls]{10}
  \multiframe{30}{ind=0+1}{
    \tikzifexternalizing{%
        Work-around to make animate happy
    }{}%
    \begin{tikzpicture}
      \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
        \addplot {sin(deg(x+\ind*pi/16))};
      \end{axis}
    \end{tikzpicture}
  }
\end{animateinline}
%
\end{document}

the statement \tikzifexternalizing is only true if one of the frames is being converted. In this case, only the picture of interest makes its way into the output pdf - and we can safely generate non-empty content (and the animate package is happy).

Answer 2

All in one approach

Read the comments whether or not you need ImageMagick and/or FFMPEG installed on your machine.

\documentclass{article}

\usepackage{filecontents}

% create a parameterized template
\begin{filecontents*}{template.tex}
\documentclass[tikz,border=12pt]{standalone}
\usepackage{pgfplots}
\begin{document}
  \foreach \ind in {1,2,...,30}
    {
    \begin{tikzpicture}
      \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
        \addplot[color=\clr]  {sin(deg(x+\ind*pi/16))};
      \end{axis}
    \end{tikzpicture}
  }
\end{document}
\end{filecontents*}


\usepackage{animate}

% creater a PDF file containing frames
%\def\param{red}
%\immediate\write18{pdflatex -jobname=frames "\def\noexpand\clr{\param} \noexpand\input{template}"}

% just another way with \unexpanded to save more keystrokes!
\def\param#1{%
\immediate\write18{\unexpanded{pdflatex -jobname=frames "\def\clr{#1} \input{template}"}}}
\param{blue}

% create a GIF animation (needs ImageMagick installed)
\immediate\write18{convert -delay 5 -loop 0 -density 100 -alpha remove frames.pdf frames.gif}

% create a list of PNG images, one for each frame (needs ImageMagick installed)
\makeatletter
\immediate\write18{convert -density 100 -alpha remove frames.pdf frames-\@percentchar02d.png}
\makeatother

% create a MP4 video (needs both ImageMagick and FFMPEG installed)
\makeatletter
\immediate\write18{convert -density 100 -alpha remove frames.pdf frames-\@percentchar02d.png}
\immediate\write18{ffmpeg -r 5 -i frames-\@percentchar02d.png -vcodec libx264 frames.mp4}
\makeatother

\begin{document}
% create a PDF animation
\begin{center}
    \animategraphics[controls,autoplay,loop,scale=1]{10}{frames}{}{}
\end{center}
\end{document}

GIF output

PNG output

I will not show all as they will waste your bandwidth.

...

Answer 3

\usepgfplotslibrary{external} and package animate don't work well together.

\tikzexternalize moves the tikzpicture environment into an external file to be processed separately (therefore, --shell-escape must be activated) and replaces the tikzpicture environment with \includegraphics.

On the first pass when no external pdf graphics are available, the boxes into which the animateinline environment stores the code it encloses have zero size. animate measures the box dimensions of the first frame and scales the animation widget accordingly. There is a built-in stop condition in animate when it finds that the box is empty.

To work-around this, consider the following code:

\documentclass{article}
\usepackage{pgfplots}
\usepackage{animate}
% Comment out the following line to see what the plot looks like.
\usepgfplotslibrary{external}

\newlength\mywidth
\newlength\myheight
\newsavebox\mybox
\begin{lrbox}{\mybox}
  \def\ind{0}%
  \begin{tikzpicture}
    \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
      \addplot {sin(deg(x+\ind*pi/16))};
    \end{axis}
  \end{tikzpicture}
\end{lrbox}
\settowidth\mywidth{\usebox\mybox}
\settoheight\myheight{\usebox\mybox}

\tikzexternalize
\begin{document}
%
\begin{animateinline}[controls]{10}
  \multiframe{30}{ind=0+1}{
    \makebox[\mywidth][l]{\rule{0pt}{\myheight}%
      \begin{tikzpicture}
        \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
          \addplot {sin(deg(x+\ind*pi/16))};
        \end{axis}
      \end{tikzpicture}%
    }
  }
\end{animateinline}
%
\end{document}

An easy way to produce a standalone, correctly sized multipage PDF of all animation frames is:

\documentclass{article}
\usepackage{pgfplots}
\usepackage{ifthen}
\usepackage[tightpage,active]{preview}
\PreviewEnvironment{tikzpicture}

\begin{document}
%
\newcounter{ind}%
\whiledo{\theind<30}{%
  \begin{tikzpicture}
    \begin{axis}[ymin=-1, ymax=1, xmin=0, xmax=3.14]
      \addplot {sin(deg(x+\theind*pi/16))};
    \end{axis}
  \end{tikzpicture}%
  \stepcounter{ind}%
  \newpage%
}
%
\end{document}

This multipage PDF can be further converted to other formats, such as SWF:

pdf2swf frames.pdf
swfcombine -r10 --output frames10fps.swf --dummy frames.swf