“Use of operation triplets” in the TWAIN 1.9 spec. It’s necessary to know about how triplets work to setup the scanner. The spec also has a list of icaps with explanations about their functionality and parameters. With that basis and the functions in EZTwain it’s easy to change parameters. It’s important to spend some time going over the TWAIN spec (at least the sections relevant to application developers).
Also download and use the TWAIN sample application from the twain.org website, it’s useful to list and test the capabilities supported in the scanner.
The ICAP you’re asking about is in the TWAIN.H file. Once you incorporate that header file to your project, if you’re using Visual Studio with autocomplete/intellisense enabled you can just type “tw” and control+space to get a list of TWAIN-related declarations.
To use the library with no UI displaying, check the EZTwain functions TWAIN_SetHideUI and TWAIN_SetIndicators.
The functions declared in EZTWAIN.H are also a good way to learn how to program TWAIN.