(v13) Modular screening interfaces

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP

The Harlequin RIP has dedicated modular Screening interfaces to the core RIP. The clients of the screening interfaces are referred to in this section as screening modules .

Screening modules are principally required to perform Raster halftoning, but they can also choose to receive object-type information for the raster to enable them to vary their screening techniques accordingly. In this role, they are more than simple rasterizers.

Areas of the raster halftoned using the screening interfaces are referred to as modular screened to differentiate them from the RIP’s built-in screening.

The operation of the screening interfaces revolves around the following main stages, each discussed in more detail throughout this section:

(v13) Module registration	This stage only declares a screening module as being available to the core-RIP, although security checks are applied at this point. Module registration happens only once.
(v13) Halftone select	This stage occurs when the PDL requests the use of a halftone, for example a PostScript language `sethalftone` operator. Separate halftone selects may be made for each potential colorant. Halftone select and release occur as necessary.
(v13) Halftone release	This occurs when an individual halftone is no longer needed. Halftone select and release occur as necessary.
(v13) Render initiation	This is where the screening module gets ready to begin halftoning. Any additional memory requirements must be allocated at this point. This step repeats for each page or separation being output.
(v13) DoHalftone	This is where the RIP asks a screening module to halftone part of a band of raster pixels. This step is repeated many times during output of a page or separation. See (v13) DoHalftone
(v13) Render completion	This gives the screening module an opportunity to free any memory it allocated at (v13) Render initiation This step repeats for each page or separation being output
(v13) AbortHalftone	This is used the to stop the module rendering an outstanding request issued by DoHalftone(). This occurs if the RIP's renderer needs to inform a screening module that the RIP needs to abort the halftoning process for a particular DoHalftone request. AbortHalftone only occurs when rendering is aborted. See (v13) AbortHalftone
(v13) Latency	A modular screen can specify its latency. That is, how many earlier bands it needs available (and may modify); see (v13) Latency .