Unless you are using high-level L_WiaAcquireSimple function, you should first initialize a WIA session before using the features available in the LEADTOOLS WIA toolkit. This is done by call the L_WiaInitSession function. The L_WiaInitSession function initializes the session with multi-threading. Each call to this function will create a session handle of type HWIASESSION. This handle is passed to many of the LEADTOOLS WIA C API functions, so this function must be called before calling other LEADTOOLS WIA functions (except L_WiaAcquireSimple). Note that for each call to L_WiaInitSession there must be a call to L_WiaEndSession.
WIA does not have a default device selection capability. Therefore, after establishing the WIA session handle, it is recommended that you select the WIA source to be used for acquiring images. For more information, refer to Managing WIA Sources.