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\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{varwidth}
\begin{document}
\begin{figure}[h]
\begin{varwidth}{\linewidth}
\includegraphics[width=0.5\textwidth]{example-image-duck}
\caption{Caption}
\end{varwidth}
\end{figure}
\end{document}
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\begin{figure}
\includegraphics[width=\textwidth]{Picture}
\caption{Picture caption}
\end{figure}