[tex-live] How to specify `scaled' parameter for \xetexpicfile

[Steven Woody]

Hi,

I am using \xetexpicfile to include a jpg file, but I get problem when
specify the `scaled' parameter.  if I use `scaled 100', then I get a
very small image, so I have to experiment many time before I know
scaled 600 is a suitable value.   So I think my question should be, if
the image size is H x V in pixel, how should I specify the `scaled'
parameter to have the image just as width as the \textwidth?

Thank you.

-
narke