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WIA Scanner Devices in WIA 1.0

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Note

This topic discusses the scanner device tree for applications that use the Windows Image Acquisition (WIA) 1.0 service (which is supported on Windows XP or earlier). For information on the device tree of Windows Image Acquisition (WIA) 2.0 items (which are supported on Windows Vista or later), see About the IWiaItem2 Item Tree.

 

The Windows Image Acquisition (WIA) scanner device is implemented as a hierarchical tree of IWiaItem objects. From the root item an application may:

  • Query scanner capabilities
  • Set scanner device properties
  • Control the document feeder

A WIA scanner device is different from a WIA camera device because, in general, it does not store multiple images in memory.

Underneath the root item, a typical scanner object has a single IWiaItem object that represents the data collecting functionality of the device, the Scan Item. This item has the WiaItemTypeFile flag set to indicate that data transfers on this item are possible. An application sets up a scan by setting the properties of the scan item, then performs the scan and transfers the data using a data transfer interface.

The following diagram illustrates the WIA implementation for a typical scanner:

wia implementation of a typical scanner

A typical duplex scanner is represented in WIA by having one IWiaItem object. Front- and back-page data is accessed sequentially one data transfer per page. Therefore, the representation of a duplex scanner is identical to the representation of a typical scanner.

A slide scanner capable of scanning multiple slides in a single scan operation represents each separate image as a separate IWiaItem object.

The following diagram illustrates the WIA representation of a slide scanner:

slide scanner