Saving multiple pages on cancellation/failure

With DTWAIN, you can save multiple pages to a single image file if there is for some reason a cancellation or failure during the acquisition process.

The DTWAIN_SetMultipageScanMode using the DTWAIN_FILESAVE_SAVEINCOMPLETE flag allows DTWAIN to save the current set of acquired pages to a file on cancellation or failure of the acquisition. By default, DTWAIN does not save multipage image files if the acquisition has been canceled (either by the user, application, or the TWAIN driver).