\tikzexternalize together with drawing on an image with TikZ

Question

I am following this very good answer that explains how to draw on an image with TikZ. Now I tried to implement this new tikz picture I got with Tikz library external but I get the error

Package tikz Error: Sorry, the system call 'pdflatex -shell-escape -halt-on-e rror -interaction=batchmode -jobname "tikz/myTikzFileName" did NOT result in a usable output file 'tikz/myTikzFileName' (expected one of .pdf:.jpg:.jpeg:.png:).

I have been working for the last time on a project with ~20 figures, all made with tikz and pgfplots, and the externalization commands worked perfect, up until now when I inserted a png file into tikz.

The graphics I want to insert into my document is the file myGraphics.tikz,

% myGraphics.tikz
\begin{tikzpicture}
    \node[anchor=south west,inner sep=0] (image) at (0,0) {\includegraphics[width=0.9\textwidth]{some-image.png}};
    \begin{scope}[x={(image.south east)},y={(image.north west)}]
        \draw[red,ultra thick,rounded corners] (0.62,0.65) rectangle (0.78,0.75);
    \end{scope}
\end{tikzpicture}

implemented with the tikzscale package:

% main.tex
\documentclass[dvipsnames]{beamer}
\usepackage{tikz,tikzscale}
%% To reduce compilation time
\usetikzlibrary{external}
\tikzexternalize[prefix=tikz]

\begin{document}

\begin{frame}{Lorem Ipsum}{dolor sit amet}
Some text
\begin{figure}
\tikzsetnextfilename{myExternalTikzFile}
\includegraphics[height=100pt]{myGraphics}
\end{figure}
\end{frame}

\end{document}

I do get a non empty md5 file, but nothing more.

Do anyone know how to fix this?

(some-image.png is this image)

Answer 1

I see two possible problems in creating your output file:

• the use of \includegraphics to invoke the .tikz file; it should rather be something like \input (see @sheß answer)
• maybe you don't use --shell-escape option when running the document; you need something like pdflatex -synctex=1 -interaction=nonstopmode --shell-escape main.tex.

I insert the code below, but the important parts of it are borrowed from sheß's answer.

The code

\documentclass[11pt]{article}
\usepackage{tikz, tikzscale}

%% To reduce compilation time
\usetikzlibrary{external}
\tikzexternalize[prefix=tikz]
\newcommand{\inputtikz}[1]{\tikzsetnextfilename{#1}\input{#1.tikz}}

\usepackage{lipsum}
\begin{document}

\lipsum[1]

\begin{figure}[htb!]
  \centering
  \inputtikz{myGraphics}
  \caption{Boletus nubes}
  \label{fig:1}
\end{figure}

\lipsum[2]
\end{document}