Once the image has been inserted into Visio it is no longer in JPEG format but some
internal format that MS do not release (as far as I know).
These newsgroups are no longer in use and it is unlikely that you will get an answer here.
There are replacement forums for Visio, Microsoft's own:
or (probably the best option for a commercial post) Visio MVP VisioGuy
Regards, Paul Herber, Sandrila Ltd.
Electronics for Visio http://www.sandrila.co.uk/visio-electronics/
Electrical for Visio http://www.sandrila.co.uk/visio-electrical/
Electronics Packages for Visio http://www.sandrila.co.uk/visio-electronics-packages/
TTL for Visio http://www.sandrila.co.uk/visio-ttl/
CMOS for Visio http://www.sandrila.co.uk/visio-cmos/