Object-based color management

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

Object-based color management should only be used when necessary because of the risk of artifacts in the output. But when carefully used, it can achieve results that are impossible any other way.

Many of the controls in the color management operators can be applied on specific object types. There are four object types which allows these controls to have different settings for each object type. Some of these controls can also be applied to objects painted in specific color models. There are five color models, allowing different settings for the twenty possible combinations of object type and color model.

A Default object type and color model may be used to avoid explicitly setting all object-based values. If a Default key is not used and not all values are explicitly set, the default for the object-based control is assumed for missing values.

One of the most common uses of object-based color management is the control of rendering intent. In the graphic arts, it is common to apply the perceptual rendering intent to RGB images, whilst all other objects use relative colorimetric. Another possible use is for object-based screening, which requires separate output profiles for each screen. A third possibility is to preserve pure colors in linework, whilst allowing images and non-pure linework to be color managed as normal. Many other uses are possible.

All of the object-based controls are keys in setinterceptcolorspace (see The setinterceptcolorspace operator and The setreproduction operator ).

The color model of an object may be modified in the context of a transparency job. Compositing a transparency group’s objects results in a backdrop raster. In any further color transform into a parent transparency group, the object type of a pixel within the backdrop is derived a top-most object wins rule; whilst the color model is normally assumed from the group’s blend space. This is fully described in Object-based color management in transparency .