Have you ever wanted to scan an image under Linux? If so, you probably know the feeling of being faced by a bewildering number of scanner-driver packages. At the time of this writing, there exist at least fourteen different scanner packages for Linux. While each individual package is usually of high quality, it is often difficult to determine which package should be used for which scanner. Furthermore, some packages come with a command-line interface, others include tcl/tk based graphical front ends, still others come with full-featured, graphical front ends. While variety is said to make life sweet, in this case it's more likely to cause a sizeable headache.
SANE was created to provide a solution to this dilemma. The basic idea is simple: if there were a general and well-defined application programming interface (API), it would be easy to write applications independently from scanner drivers. Thus, the author of a new scanner driver would not have to worry about writing an application for the driver. There are benefits for the application programmer as well; since SANE is universal, an application can be written independently of the devices that it will eventually control. Suppose we wanted five applications to support ten different devices. With the old approach, 5*10=50 programs would have to be written. With SANE, only 5+10=15 programs have to be written. SANE has advantages for the user too. It gives the user the liberty to choose whichever application he likes best, and that one application can be used to control all image-acquisition devices the user can access. Thus, SANE makes it possible to present the same consistent interface independent of the particular device that is in use.
Of course, SANE is not the first attempt to create such a universal interface. You may have heard of TWAIN, PINT or the Linux hand-scanner interface. The problem is that these older interfaces prove to be lacking in one way or another. For example, PINT is really a somewhat primitive kernel-level interface and the hand-scanner interface by definition is limited to hand-scanners. In contrast, SANE is general enough to support any device that acquires raster images. The closest thing to SANE is probably TWAIN. The fact that the two rhyme is not coincidental, but that's a different story. The main reason TWAIN is not SANE is that TWAIN puts the graphical user-interface to control the device in the driver instead of the application. This makes it unsuitable for Linux or networked environments where the scanner driver might run on one machine and the application on another. In contrast, SANE enforces a strict separation between the actual driver and the user-interface for its controls. Indeed, the current SANE distribution includes support for network-transparent scanning.