Basic idea

Basic structure

Basic API structure is shown on image. Most important parts of API are:

• Engines: responsible for physical creation of derivatives. Engines are implemented as own modules. API itself does not implement any engine functionalities, it only provides hooks for them.
• Conditions: their responsibility is to decide, if a given file should be derivated with a given preset at a given time. Few basic conditions are implemented in API itself. Hooks are provided to allow custom modules to implement own custom rules.
• Events: events are executed when a file's derivative should be created. API implements two basic events, that are executed when a file is uploaded and when a file was added to a file/media/image field. Hooks are provided, that allow other modules to provide custom triggers.
• Presets: presets are responsible for configuration, that is used to create a derivative of a given file. Presets are based on CTools export API. Presets can be defined in code or in UI (and later exported to code/feature)
• Schedulers: scheduler's responsibility is to run derivation of a file at the right time. API currently implements three simple, time-based schedulers. Hooks are provided, that allow other modules to provide custom schedulers.

Derivative is saved in file_managed table if successfully created.