(v13) Transparency color management

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

Transparency effects may appear in PDF. As far as color management is concerned, the important feature is the transparency group, which contains a collection of objects which are composited together in a common color space called the blend space. The presence of a transparency group implies an extra color transform that needs to be applied to a graphical object. Transparency groups may be nested to any depth to form a transparency group stack.

Within a transparency group, objects are color converted to the group’s blend space before compositing. The result of compositing is a backdrop, a raster, which is at device resolution. With nested transparency groups, backdrop rasters are color converted into their parent transparency groups.

In the RIP, color transforms, both into a transparency group and between groups, allow color management similar to that described in (v13) ICC color management for non-transparency ICC color management. There are necessary differences which are explained in the rest of this section.