The TWAIN2 Sample Application displays the ExtImageInfo including barcode strings from the scanner.
It will either retrieve all advertised ExtImageInfo or if the DS does not support ICAP_SUPPORTEDEXTIMAGEINFO it will attempt a small set of known types that includes TWEI_BARCODETEXT.
https://sourceforge.net/projects/twain-samples/files/TWAIN%202%20Sample%20Application/
Regards,
Jim Watters
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