MFCN 1.1.1000.1 (intron):

"So that JADE can find built PNG images while building a single
book in its own directory. But there's a bug:

If I build book.rtf only, PNG images will not be built.
I have to build book.rtf after building book.html."

Submitted by: "intron" <intron intron ac>
Obtained from: The FreeBSD Simplified Chinese Project