像这样:
您需要在图像的垂直中心设置基线:
\documentclass{article}
\usepackage[export]{adjustbox} % <---
\begin{document}
\begin{center}
\includegraphics[scale=0.33, valign=m]{example-image-a}
$\longrightarrow$
\includegraphics[scale=0.33, valign=m]{example-image-b}
\end{center}
\end{document}