Specifying color output capabilities

This page applies to Harlequin v13.1r0 and later; and to Harlequin Core but not Harlequin MultiRIP.

This section concerns specifying the color channels of a printing device, and their capabilities. It is mostly useful for composite devices:

• It is important to understand the difference between the output colorants, as produced by the RIP, and the color channels available on the printing device. The output colorants are produced by the RIP and typically specified by the ProcessColorModel, SeparationColorNames, and SeparationOrder keys of the setpagedevice operator. The color channels are a feature of the printing device. When rendering the output rasters, the RIP maps the output colorants onto the color channels. Details of the other setpagedevice keys that control the output color format are in Color format control keys and SeparationDetails.
• One obvious class distinction can be made between composite vs. separating devices:
  • Composite devices have multiple channels, usually with a one-to-one mapping between output colorants and the color channels, with data for all colorants sent to the device in a single raster. While the RIP's default settings are sometimes sufficient, it is commonly necessary to configure the color channels of a particular composite device.
  • Separating devices can be considered as two separate devices working together to produce the finished output; the primary device (for example, a platesetter), and the printing press. The primary device normally only has one, Gray, color channel, with the separations for each output colorant sent to it in turn producing one raster per colorant. The printing press converts the Gray rasters to the final colors. While the RIP requires configuration of the color channels for both the primary device and the printing press, the RIP's default settings are normally sufficient, so most separating devices don't need their own configuration.

The color channels of all printing devices known to the RIP are configured by the ColorantFamilies entry of the SeparationDetails sub-dictionary supplied to the setpagedevice operator. We recommend that they are configured during the boot-up process (for example in the Sys\HqnOEM file but may be put in job-specific configuration PostScript). In addition, each printing device may support multiple variants of color channels (for example, a CMYK plus four spots device) may also support CMYK plus one, two, or three spots. These variants may need their color channels configuring independently.

The ColorantFamilies entry contains an organized collection of Colorants arrays, each of which defines of a particular fixed set of device channels, their properties, and the names of the inks, varnishes, primers, and so forth that are represented by those channels.

The Colorants arrays are associated with a printing device by their parallel Plugin and DeviceType keys. This allows the Colorants arrays for all printing devices to be defined at the same time during RIP boot-up. The Plugin/DeviceType key combination need not be unique to one Colorants array, but if more than one does have the same keys, they should have different colorants.

For historical reasons, both the Plugin and DeviceType keys are used to associate a Colorants array with a printing device. Their values have no semantic meaning in the Harlequin Core SDK; they are just keys used for the selection of an appropriate Colorants array for a given printing device.

For historical reasons, Colorants arrays are conventionally organized using a ColorantFamilyName that matches the ProcessColorModel, but there is no other reason for doing so.

As part of the setpagedevice operator, the most appropriate Colorants array is selected  from the whole of ColorantFamilies. Specifically, the selection is based on these criteria:

• The associated Plugin and DeviceType values must match the corresponding values in the pagedevice.
• It must contain all colorants implied by ProcessColorModel.
• All colorants in the Colorants array must be either in SeparationColorNames, or implied by ProcessColorModel.
• If there is more than one matching Colorants array, the one selected is the one with the largest number of colorants matching SeparationColorNames.

For separating devices (that is, if the SeparationStyle is 1, black separations), most color channel properties are taken from the Colorants array selected above, which is used for the properties of the colorants on the printing press. However, the Presence key is taken from a second Colorants array selected for the primary device, whose selection is based on these criteria:

• The associated Plugin and DeviceType values must match the corresponding values in the pagedevice.
• All colorants in the Colorants array must be in CompositeColorNames.
• If there is more than one matching Colorants array, the one selected is the one with the largest number of colorants matching CompositeColorNames.

A printing device may support a variable number of extra device channels for spot colorants. Such channels may have their own properties.

The Harlequin Core SDK has a default setting for ColorantFamilies that recognizes DeviceCMYK, DeviceRGB, and DeviceGray devices. However, we recommend that customers add their own entries to the DeviceTypes dictionary for composite devices.