OpenFX (API)

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OpenFX (OFX), a.k.a. The OFX Image Effect Plug-in API, is an open standard for 2D visual effects or compositing plug-ins. It allows plug-ins written to the standard to work on any application that supports the standard. The OpenFX standard is owned by The Open Effects Association, and it is released under a 'BSD' open source license. OpenFX was originally designed by Bruno Nicoletti at The Foundry Visionmongers.

Plug-ins are written as dynamic shared objects, and the API specifies a few entry points that must be implemented by the plug-in.

The OpenFX host exposes sets of entry points to the plug-in, called suites. The Property Suite is used to manage attribute-value pairs attached to objects defined by all other suites of the API, the Image Effect Suite is used to fetch film frames from the inputs or the output of the effect, and there are other suites to display informative messages or ask questions to the user, handle multithreading, use OpenGL for processing, etc.

Each plugin is described by a list of parameters and supported inputs and output. The host may execute various actions, for example to signal that a parameter value has changed or that a portion of a film frame has to be rendered.

Optionally, the plug-in may also display graphical information over the current frame using OpenGL, and propose interactions using mouse and keyboard (this is called interacts in the OFX specification).

An OpenFX host is an application capable of loading and executing OpenFX plugins.