Is there a way to get an image from a usb scanner (on Windows primarily, cross-platform solution would be best) and post the image together to a form in browser with Flex or Java applet?
thx!
The standardized TWAIN scanning interface is definitely the place for you to look at, rather than low-level USB, except if you are targeting only one specific device and know how to talk to it.
Java based
There is another Stack Overflow question pointing out a link to a open Applet talking to a TWAIN device. If you're looking to spend no money, and build it yourself, that is maybe a starting point.
The only ready-made commercial product on the market that I can see is JTwain. I don't have any TWAIN devices handy to test, but it looks good.
TWAIN seems be on its way to Linux as well, and the makers of the commercial product promise support for other platforms in the future.
Active X / Plugin-based
There is at least one product connecting Twain on a Windows-only, ActiveX/Browser plugin basis, claiming to support all major browsers. A 30-day trial version is available.