Base64 LaTeX example

mydoc.tex

\documentclass{article}
\usepackage{filecontents}
\usepackage{graphicx}

\newcommand{\generateimage}[2]{%
\immediate\write18{convert.cmd #1 > #2}}

\begin{document}

\begin{filecontents*}{myfigure.txt}
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
\end{filecontents*}

Hello there.

\generateimage{myfigure.txt}{myfigure.png}
\includegraphics{myfigure.png}

\end{document}