This is called ‘push model’ – where the scan is initiated from the scanner instead of from the application.
I’m sure others know more about this than I do, but I have two suggestions:
In your code, open the scanner and poll the scanner for feeder loaded (ICAP_FEEDERLOADED) and when it shows true, wait a moment (in case user is straightening the paper) and then start a scan. User doesn’t even have to push a button. But only works if the scanner can (silently) poll and report feeder loaded.
Check out ‘STI’ – this is an older Microsoft scanner API, the ancestor of WIA. It allows scanners to generate events like button-presses, and applications (like yours) can register to receive notice of those events.
Or at least, an app can be launched… so you might have to have a little mini-app that gets launched on the button-press, and it sends a message to your main app…
Try google for STI scanner button press
Whoo! Found a guy who does his own STI registration by filling in the registry entries – muy macho:
http://icopy.sourceforge.net/?p=98