Editing Image scanner (section)

=== Applications programming interface {{anchor|Applications Programming Interface}} ===
A raster image editor must be able to communicate with a scanner. There are many different scanners, and many of those scanners use different protocols. In order to simplify applications programming, some [[application programming interface]]s (APIs) were developed. The API presents a uniform interface to the scanner. This means that the application does not need to know the specific details of the scanner in order to access it directly. For example, [[Adobe Photoshop]] supports the [[TWAIN]] standard; therefore in theory Photoshop can acquire an image from any scanner that has a TWAIN driver.<!--GIMP + SANE?-->

In practice, there are often problems with an application communicating with a scanner. Either the application or the scanner manufacturer (or both) may have faults in their implementation of the API.

Typically, the API is implemented as a [[Library (computing)|dynamically linked library]]. Each scanner manufacturer provides software that translates the API procedure calls into primitive commands that are issued to a hardware controller (such as the SCSI, USB, or FireWire controller). The manufacturer's part of the API is commonly called a [[device driver]], but that designation is not strictly accurate: the API does not run in kernel mode and does not directly access the device. Rather the scanner API library translates application requests into hardware requests.

Common scanner software API include:

* [[TWAIN]]&nbsp;– An API used by most scanners. Originally used for low-end and home-use equipment, it is now widely used for large-volume scanning.
* [[Scanner Access Now Easy|SANE (Scanner Access Now Easy)]]&nbsp;– A [[Free software|free]]/[[Open-source model|open-source]] API for accessing scanners. Originally developed for [[Unix]] and [[Linux]] operating systems, it has been ported to [[OS/2]], [[macOS|Mac OS X]], and [[Microsoft Windows]]. Unlike TWAIN, SANE does not handle the user interface. This allows batch scans and transparent network access without any special support from the device driver.
* [[Windows Image Acquisition|Windows Image Acquisition (WIA)]]&nbsp;– An API provided by Microsoft for use on [[Microsoft Windows]].
* [[Image and Scanner Interface Specification|Image and Scanner Interface Specification (ISIS)]]&nbsp;– Created by Pixel Translations, which still uses [[SCSI-2]] for performance reasons, ISIS is used by large, departmental-scale, machines.