(v13) Types of input plugin

This page applies to Harlequin v13.1r0 and later; and to Harlequin MultiRIP but not Harlequin Core

Input plugins provide data communications between the RIP and the outside world. They allow the input and output of arbitrary data.

The SDK includes several examples of input plugins, including a repeating “Hello World” job generator, a font query generator, a uudecoding filter, and a progress device.

The interface between an input plugin and the RIP forms an abstract model of input and output. The details of communication with a particular piece of hardware - such as a serial port, SCSI device, or accelerator board; or with a software protocol, such as AppleTalk - can be hidden from the RIP inside the input plugin. This enables you to write an interface to an arbitrary communication medium, entirely independent of the RIP.

There are a number of types of input plugin. An input plugin can:

• Serve as a source of PostScript language jobs for the RIP to interpret. (The majority of input plugins do this.)
• Support files, opened explicitly from the PostScript language, that are stored in some specialized way. (For example, an input plugin could implement an Open Prepress Interface (OPI) server, with the high‐resolution files being accessed from a database.)
• Provide custom PostScript Level 2 filters that implement data translation algorithms, possibly with hardware assistance.
• The RIP's built‐in filters may be replaced. For example, the built‐in implementation of the DCT J‐ PEG decoding filter could be replaced by an accelerator board which did the same job and an input plugin to interface it to the RIP.
• Implement asynchronous actions : specialized, usually short, PostScript language jobs which are executed at unpredictable times, often while the RIP is busy running another job. Typically, they provide answers to queries from the interpreter or perform filing operations.

For example, an asynchronous action could provide a list of the fonts currently installed (in such a case, you would need to take care not to include transient fonts introduced by the job in progress) or install a new file on the disk, perhaps to add a page buffer to the Output Controller.

• Implement progress devices that show how the RIP is progressing through its current job. The RIP generates progress information during interpretation that can be intercepted and presented as you see fit. Note that the progress device is now replaced by timelines. For more information see Timelines .