Which is better practice: rendering figures on the fly, or importing them as images?

Question

I've come to a philosophical quandary with respect to my use of LaTeX for scientific writeups. At first I tried to render all figures in LaTeX at compile-time, for example making a graph using PGFPlots instead of importing it from Excel. However as I started bigger projects my compile time got exponentially larger, and I heard that many prefer pre-rendered images in figures rather than figures rendered at compile-time. Which is better practice for large projects with many diagrams?

The project I'm working on now includes a couple of graphs and circuit diagrams in circuitikz, for a certain degree of context. I also am considering taking figures designed in LaTeX, exporting them as images, then reimporting them into the final document. Thanks.

Answer 1

standalone can be set up to recompile included pictures only if required. Otherwise, it will include the previously compiled PDF. So it is not necessary to switch to \includegraphics to benefit from pre-compilation.

Here's a basic example.

The figure:

% mytikz.tex
\documentclass[tikz,border=5pt]{standalone}
\usetikzlibrary{cathod}
\begin{document}
  \begin{tikzpicture}
    \pic {cath gorwedd={blue!50}{blue!25}{green}{yellow}{red!20!brown}};
  \end{tikzpicture}
\end{document}

All that is really necessary here is the tikzpicture environment but the rest is handy while working on the image initially and standalone will ignore it when appropriate, so it might as well stay.

Now the main file:

\documentclass{article}
\usepackage[mode=buildnew]{standalone}
\usepackage{tikz}
\usetikzlibrary{cathod}
\begin{document}
  \begin{figure}
    \includestandalone{mytikz}
  \end{figure}
\end{document}

Provided compilation is done with -shell-escape, the following will happen:

• on the first run, a separate compilation process will run to create a cropped version of the image, mytikz.pdf which will then be included with \includegraphics{};
• on subsequent runs, the image will be included using \includegraphics{} unless the source has changed, in which case it will be recompiled first.

By altering the value of mode=, this behaviour can be customised as required.

In all cases, I get a lovely blue cat:

However, you can use it with pictures of other cats, too. Even non-cat content works, or so I've been given to understand.

An alternative is to use the external TikZ library to externalise images. Again, this requires -shell-escape and it can be configured. By default, it also recompiles a figure only if it has changed. However, this is obviously limited to PGF/TikZ pictures whereas standalone provides a more generalised approach.

Answer 2

It seems to me that publications will mostly want pre-compiled graphics. You can ease your quandary relatively painlessly by moving your preamble and Tikz/PGF graphics to separate .tex files and use \input to give yourself a choice at compile time. For instance, your main document might look like:

\documentclass{report}
\input{preamble}
\begin{document}
\begin{figure}
  %\includegraphics{pgf_graphic.pdf}
  \input{pgf_graphic.tex}
  \caption{\label{fig:...}...}
\end{figure}
\end{document}

and if you want to pre-compile, you make a wrapper for your graphic like:

\documentclass{standalone}
\input{preamble}
\begin{document}
\input{pgf_graphic.tex}
\end{document}

then, you can swap the comments on the lines with \input{pgf... with the \includegraphics{pgf... in the main document based on need, mood, etc...

I do this, but I am still trying to settle on the best file structure to make the workflow seamless.

Answer 3

I am currently updating an illustrated dictionary of mathematical concepts. It includes a lot of 3D graphs and I knew that the compilation time was going to increase drastically if just leave the source code and generate them all each time the document is compiled.

So my solution was this:

I created a separate tex file, called "DrawTest.tex" in order to write the source code for the graphs and figures that are to be included in the dictionary. Once I am satisfied with the way the figure looks like, I generate two files: a PDF with the figure and a source code file without the preamble and the \end{document} line. Both files have to have the same name. And by means of the following instruction:

%
% Instruction to decide if a PDF has to be added 
% or the corresponding source code
%
\newcounter{final}
\setcounter{final}{0}
\newcommand{\insertfigure}[1]{
    \ifthenelse{\thefinal=1}{\input{./source/#1}}{\pgfimage{./gallery/#1.pdf}}
}

when I create the PDF corresponding to the draft of the dictionary, the PDF files are inserted as images. When I am done with the whole document (i.e., when I finish the dictionary), the last time I am going to generate it, I just need to switch the value of the counter final, (I usually change it to zero) and the figures are generated from its latex source code.

From the previous code, it goes without saying that the tex files are saved into a folder called "source" and the PDF's are located at the folder named "gallery".

The source code for the file "DrawTest.tex" is something like:

\documentclass{article}
\usepackage{tikz}
\usepackage{tikz-3dplot}
\usetikzlibrary{math}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{0.1pt}
%
\begin{document}
%
\begin{center}
%
\begin{tikzpicture}
  % Include here the lines of code for the figure.
\end{tikzpicture}
\end{center}
%
\end{document}

Generate the PDF file for the figure, and copy the PDF into the folder "gallery". And from that code, just delete the preamble, including the \begin{document} line, together with the last line, including the \end{document} instruction, and that is the file that is needed in the folder titled "source". Just remember to name both files exactly equal.

This is the way I use to avoid time consumption because of the compilation of the figures.

If anybody comes up with a better approach, I will be glad to copy the strategy.