This Section defines version 2 of the SANE application
programmer interface (API). Any SANE frontend must depend on the
interface defined in this section only. Converseley, any SANE backend
must implement its functionality in accordance with this
specification. The interface as documented here is declared as a C
callable interface in a file called sane/sane-2.h. This file should
normally be included via a C pre-processor directive of the form:
#include <sane/sane-2.h>