WIA Core Components

The WIA components for Windows XP and Windows Me are shown in the following figure.

diagram illustrating windows xp and windows me core components

The WIA Service (wiaservc.dll) is hosted by a generic host called svchost.exe in Windows XP and stimon.exe in Windows Me. Wiaservc.dll communicates with one or more user-mode still image drivers (labeled USD1, USD2, and USD3 in the figure), each of which communicates with a particular type of kernel-mode driver. Windows XP and Windows Me provide three types of bus abstraction: USB, SCSI, and serial ( usbscan.sys, scsiscan.sys, and serscan.sys).

On the client side, an application can be either a TWAIN-compatible application (see Support for TWAIN-Compatible Applications) or a WIA application. A TWAIN application calls into the data source manager, which in turn calls into wiadss.dll, a translation component that communicates with an instance of sti.dll. Sti.dll is a stub that communicates with the WIA service. In contrast, a WIA application makes calls directly to sti.dll.

Windows 98 and Windows 2000 do not support WIA. Their STI core components can be seen on Windows 98 Core Components and Windows 2000 Core Components.

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