>>331
そうなんだ。うちはbbを指定しないとエラーになるよ。
$ cat tmp01.tex
\documentclass{jsarticle}
\usepackage[dvipdfmx]{graphicx}
\begin{document}
\includegraphics[width=\textwidth]{16.png}
\end{document}
$ platex tmp01.tex
This is e-pTeX, Version 3.1415926-p3.4-110825-2.6 (utf8.euc) (TeX Live 2013/Debian)
restricted \write18 enabled.
[snip]
! LaTeX Error: File `16.xbb' not found. Use -shell-escape option to generate au
tomatically.

See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...

l.4 \includegraphics[width=\textwidth]{16.png}