Knockouts and overprinting

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

A knockout is a white hole produced in one color separation by the presence of a colored object in another separation. If the hole were not there, the ink in the first separation would mix with the ink in the other to produce a mixture which is usually not the color originally intended.

Overprinting, the mixing of color separations from different graphical objects, is sometimes intended. Overprinting is normally controlled by the op, OP and OPM, graphics state PDF attributes, and the PostScript equivalent operators of setoverprint and setoverprintmode. However, these don't give enough control for some purposes, so the Harlequin RIP has extensions to more finely control overprinting, as detailed in this section.

In addtion, the KnockoutType entry in the colorants array that controls whether a color separation should never knockout, and/or never be knocked out by other objects. This is described in SeparationDetails keys affecting colorant families.