Hello the team,
it's me again.
This time I would report a bug of XeTeX about DPI.
If one tries to insert two figure with different DPI, XeTeX will fail to handle the bounding box.
See the mwe:
\documentclass{article}
\usepackage{graphicx}
\usepackage{showframe}
\begin{document}
\begin{figure}[!htb]
\centering
\begin{minipage}{0.5\linewidth}
\centering
\includegraphics[width = \linewidth]{example-image-90dpi.jpg}
\caption{90 dpi}
\end{minipage}%
\begin{minipage}{0.5\linewidth}
\centering
\includegraphics[width = \linewidth]{example-image-100dpi.jpg}
\caption{100 dpi}
\end{minipage}
\end{figure}
\end{document}
The two .jpg files could be found at my website.
http://liam0205.me/attachment/LaTeX-useful-tools/dpi-issue.zip
Anonymous