Image matrix using the whole line width?

Question

This works to create a nice matrix, but rather than selecting the width, can I automatically make it scale to full line width, by setting a width percentage in one image, or do have to use width=0.25\textwidth in every line?

\begin{figure}[h]
\begin{center}$
\begin{array}{cccc}
\includegraphics[width=1in]{image1} &
\includegraphics[width=1in]{image2} \\ 
\includegraphics[width=1in]{image3} &
\includegraphics[width=1in]{image4} 
\end{array}$
\end{center}
\caption{my caption}
\end{figure}

Answer 1

Yes, it can be done with \resizebox.

I also use a trick for making the space between the figures the same horizontally and vertically.

\documentclass{article}
\usepackage{graphicx,booktabs}

\usepackage{lipsum}

\begin{document}

\lipsum[3]

\begin{figure}[htp] % not just h
\centering % not center

\resizebox{\textwidth}{!}{%
  \renewcommand{\arraystretch}{0}%
  \begin{tabular}{@{}c@{\hspace{3pt}}c@{}}
  \includegraphics[width=1in]{example-image.pdf} &
  \includegraphics[width=1in]{example-image-a.pdf} \\
  \addlinespace[3pt]
  \includegraphics[width=1in]{example-image-b.pdf} &
  \includegraphics[width=1in]{example-image-c.pdf} 
  \end{tabular}% <-- don't forget
}

\caption{my caption}

\end{figure}

\lipsum[4]

\end{document}

For 3 by 3 arrangement it is similar.

\documentclass{article}
\usepackage{graphicx,booktabs}

\usepackage{lipsum}

\begin{document}

\lipsum[3]

\begin{figure}[htp] % not just h
\centering % not center

\resizebox{\textwidth}{!}{%
  \renewcommand{\arraystretch}{0}%
  \begin{tabular}{@{}c@{\hspace{3pt}}c@{\hspace{3pt}}c@{}}
  \includegraphics[width=1in]{example-image.pdf} &
  \includegraphics[width=1in]{example-image.pdf} &
  \includegraphics[width=1in]{example-image-a.pdf} \\
  \addlinespace[3pt]
  \includegraphics[width=1in]{example-image-b.pdf} &
  \includegraphics[width=1in]{example-image-b.pdf} &
  \includegraphics[width=1in]{example-image-c.pdf} \\
  \addlinespace[3pt]
  \includegraphics[width=1in]{example-image-b.pdf} &
  \includegraphics[width=1in]{example-image-b.pdf} &
  \includegraphics[width=1in]{example-image-c.pdf} 
  \end{tabular}% <-- don't forget
}

\caption{my caption}

\end{figure}

\lipsum[4]

\end{document}