Photoshop plugin
Photoshop plugins (or plug-ins) are add-on programs aimed at providing additional image effects or performing tasks that are impossible or hard to fulfill using Adobe Photoshop alone. Plugins can be opened from within Photoshop and several other image editing programs (compatible with the appropriate Adobe specifications) and act like mini-editors that modify the image.
Photoshop functionality can be extended by add-on programs called Photoshop plugins (or plug-ins). Adobe creates some plugins, such as Adobe Camera Raw, but third-party companies develop most plugins, according to Adobe's specifications. Some are free and some are commercial software. Most plugins work with only Photoshop or Photoshop-compatible hosts, but a few can also be run as standalone applications.
There are various types of plugins, such as filter, export, import, selection, color correction, and automation. The most popular plugins are the filter plugins (also known as a 8bf plugins), available under the Filter menu in Photoshop. Filter plugins can either modify the current image or create content. Below are some popular types of plugins, and some well-known companies associated with them:
Color correction plugins (Alien Skin Software, Nik Software,OnOne Software,Topaz Labs Software, The Plugin Site, etc.)
Special effects plugins (Alien Skin Software, Auto FX Software, AV Bros.,Flaming Pear Software, etc.)
3D effects plugins (Andromeda Software, Strata, etc.)
Adobe Camera Raw (also known as ACR and Camera Raw) is a special plugin, supplied free by Adobe, used primarily to read and process raw image files so that the resultant images can be processed by Photoshop. It can also be used from within Adobe Bridge.
Photoshop plugin types
Photoshop-compatible plugins fall into several main types: filter plugins .8bf, import plugins (also called 'acquisition') .8ba, export plugins .8be, file format plugins .8bi, and automation plugins .8ly. Also, there are selection plugins 8bs and parser plugins 8by, but no one other than Adobe has ever created plugins of these types.
"Import/export plugins" acquire or write image data from or to certain devices, "file format plugins" open and save less common image formats (not inherently supported by Photoshop), and "automation plugins" automate certain tasks in the manner of Photoshop "actions" (macros).
Host applications or Host Photoshop plugin
Host applications or plugin hosts are graphics applications that are capable of running plugins. Many commercial graphics applications support Photoshop-compatible plugins — Photoshop, Paint Shop Pro, Photoshop Elements, PhotoImpact, Corel PhotoPaint, and Adobe Fireworks are the most renowned ones. There are several dozens more plugin hosts, including little known products like Chasys Draw IES, free editors like GIMP (with certain add-ons) and viewers like IrfanView. Much support is limited to the Microsoft Windows platform and .8bf filter plugins.
Photoshop fully supports all available plugin types; certain hosts, like Photoshop Elements, support most of them, while the majority of hosts support filter plugins only and many of them don't even support all available filter plugins.
The support for plugins was more uniform up until 2002, when Adobe restricted access to the Photoshop SDK containing the specifications for Photoshop plugins, and made the developer license more prohibitive. Since then, developers of other image applications have had limited or no access to it anymore, so they can't support newer host features. Therefore, plugin developers face a dilemma: either support the new host features that appeared in Photoshop 7 and later versions, like the access to layers, and lose the compatibility with other image applications, or use the old SDK version which already includes all important specifications and make sure the plugin will be supported by all hosts.
Around 2005, Adobe changed the policy so that developers could make the request for the SDK via a Web form with no fee charged for it and with all requests handled individually.
