The TWAIN interface lets you acquire an image from a scanner, digital camera, or other device, and import it into an application. (For example, you can use TWAIN with Adobe PageMaker or Adobe Photoshop.) The following components make up the TWAIN interface
When you choose to acquire an image in a TWAIN-compliant application, it calls the TWAIN Source Manager.
Applications that support the TWAIN interface provide the TWAIN Source Manager files. The Source Manager handles the communication between the application and the source device (for example, scanner), and loads and unloads the data source. It also displays the Select Source dialog box when more than one data source is installed. When an application calls TWAIN, the operating system loads the Source manager into memory, where it can manage multiple TWAIN-compliant applications, source devices, and data sources.
In Windows, the Source Manager file is in the Windows folder. The Source Manager files for Windows 3.1x, Windows 95, and Windows 98 areTwain.dll (for 16-bit data sources), Twain_32.dll (16-bit or 32-bit data sources), or Twain32.dll (32-bit data sources). Windows NT 4.0, a 32-bit operating system, requires the Twain32.dll file.
In Mac OS, the Source Manager file (named Source Manager) is in the System Folder:Preferences:Twain folder.
A data source, or TWAIN source, file provides information about the source device (for example, scanner) to the TWAIN-compliant application. It also provides the user interface for the source device in the application, and can serve as a driver for the source device. Data source files can even perform specific operations (for example, prescan the scanner bed). While most applications use the user interface provided by the data source file, the TWAIN specification enables applications to use their own interfaces instead.
Most source devices acquire raster, or bitmap, image data. However, TWAIN-compliant devices can acquire other data types from both peripheral and virtual devices (for example, image databases, digital cameras). You can either connect a TWAIN-compliant device directly to the host computer using a SCSI or serial connection, or connect it remotely using a network.
In Windows, the Source Manager searches for data source files (*.ds) in the Twain or Twain_32 folder, which is usually in the Windows folder. In Mac OS, the Source Manager looks for data source files in the System Folder:Preferences:Twain folder. However, many Mac OS source devices use application plug-ins that follow protocols different from TWAIN. For more information, contact the device manufacturer.
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