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#1 Posted : Monday, June 11, 2007 6:10:08 AM(UTC)

Groups: Registered
Posts: 11


I am using Leadtools Raster Imaging Pro 15.

I am developing an windows application(Developed in C# & .Net 2005) in which i have to capture the images through web cam asynchronously.

Here capturing image should be done asynchronously.  So in my application i am calling an Asynchronous method in which entire process of showing Sources list, showing manufacturer UI of selected device and capturing image will be done.

I am showing list of sources/devices by calling "TwainSession.SelectSource()" method by passing empty string.  Once user selects the appropriate device (webcam) i am showing the manufacturer UI of selected device by calling the method  "TwainSession.Acquire(TwainUserInterfaceFlags.Show | TwainUserInterfaceFlags.Modal)".   After calling this method it is showing a big blank screen which can be closed by pressing "Alt+F4" only.

But if i do the same steps in a synchronous call application is showing UI of the selected device correctly.

Would you please explain the reason to get a blank screen in Asynchronous call where as we are getting appropriate UI in Synchronous call?  And also please provide the solution to get correct UI in Asynchronous call because it is the requirement of our application.





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#2 Posted : Tuesday, June 12, 2007 12:59:47 AM(UTC)
Maen Hasan

Groups: Registered, Tech Support
Posts: 1,326

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What is the difference between the synchronous call and the Asynchronous call?
How are you doing both calls exactly? Are you doing this in a separate thread, for example?

Can you put the scanning code that doesn't work in a small working project (not your full application) and send it to me in a ZIP or RAR file?

Please note that the TwainUserInterfaceFlags.Modal flag you're using causes the Twain source UI to lock its parent window until the UI is closed.

Maen Badwan
LEADTOOLS Technical Support
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