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(v13) Screening selection criteria

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

Object type

Some systems may require that Screening be dependent upon the class or type of object. This requirement is interpreted as meaning that either:

  • Hooks such as HDLT can be used to switch the halftoning as each object or objecttype is encountered.


  • Screening modules can be provided with object-type information at pixel resolution, so that they can use their own algorithms to vary their screening.

Other criteria

The other criteria that influence the type of Screening adopted are:

  • Separation (assumed to be synonymous with colorant).
  • Color chain. An example provided contained a different screening for black and white images (embedded group).
  • Tonal value or range. An example of this are contained screens that do not follow the PostScript language monotonic pixel lighting order. Such screens may be used when tuning screening to take into account hardware peculiarities.

Separation or colorant switching is controlled using standard PostScript language halftone Type 5 features.

Black and white image screen switching is addressed by HDLT hooks.

Built-in RIP support for tonal value screen switching is not provided; a screening module must provide such capability.

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