The PostScript language does not support ICC technology. That is, it does not have constructs which allows the specification of an ICC profile in a PostScript file.

Instead, from Level 2 (1989) on, PostScript contains its own color description system and from Level 3 (to be precise, from Level 2 version 2016) on, it has its own color management system, complete with profiles, rendering intents and CMM. This system, called PostScript Color Management (PCM) operates only during printing, within a PostScript rip.

Unlike ICC technology, in which the PCS (Profile Connection Space) may be either XYZ or Lab, PCM always uses the XYZ space as connection space.

A scanner ICC profile is one-directional while other are two-directional, converting coordinates from device to PCS (Lab or XYZ) and vice versa. A PCM profile is always one-directional. There are two types of one-directional profile: color space array (CSA), converting from image to XYZ, and color rendering dictionary (CRD), converting from XYZ to device.

The CSA is thus analogous to a ICC scanner profile or to half an ICC monitor or printer profile, the part used when the profile is a source profile, "to PCS" to be precise.

The CRD is analogous to the "from PCS" part of an ICC printer profile, i.e. the part used when the profile is a destination profile.

Last, an ICC profile can have four rendering intents, while a PostScript profile can have only one rendering intent. If you want more rendering intents you must have more than one CRD.

• the code is generated from a PostScript driver (LaserWriter or AdobePS) or directly from the application (XPress, Photoshop, Freehand, etc.) and is transmitted (or saved in a .ps file and then loaded) to the rip in a print stream;
• the code is saved in an Encapsulated PostScrip file (.eps) that can be subsequently loaded directly in the rip or that can be imported in a job, inside of an application, and subsequently can be printed like part of such job;
• the code is generated from a PostScript driver, (LaserWriter or AdobePS) or directly from the application (XPress, Photoshop, Freehand, etc.), saved in a .ps or .eps file and then executed by a PostScript interpreter outside of a rip, like Acrobat Distiller, that produces a .pdf file.

When PostScript code is transferred to the rip for printing, in the printing stream the CSA, containing the information for converting colors from the source space to the XYZ space, is also inserted. Alternatively, an EPS with a built-in CSA can be saved.

A CRD that resides in the rip, contains the information to change the XYZ coordinates into the ink percentages for that printer.

When the PostScript code with its CSA arrives at the rip, the PostScript interpreter (which acts as a color engine) converts the source colors into XYZ and from XYZ to the colors of the printer. This process is defined by the rip programmer using what PostScript calls "color rendering procedures".

The selection of the suitable CRD is the task of the PostScript interpreter, which operates as programmed. Many rips allow the selection of different CRDs according to print resolution, type of paper and rendering intent.

If the PostScript printing stream or the EPS has no inserted CSA, the rip may use a default CSA. If the rip has no resident CRD, or does not wish to use it, another may be downloaded, by the operator or by the application itself.

One can use the CRD resident in the printer rip if there is one and it is usable. In this case the workflow is independent of the device, because the user need not indicate the printer profile.

Otherwise the CRD can be obtained from an ICC profile, inserted into the PostScript print stream and transmitted to the rip together with the CSA (e.g. Adobe InDesign 1.5 has the option “Download” CRD to printer).

This workflow depends on the device because the user must indicate what the ICC profile for the printer is, and the same profile cannot be sent to a different printer.

In each case, the color management occurs in-rip, with a conversion between source CSA and destination CRD.

Both techniques have advantages and disadvantages, which includes:

• resident CRD:
  • pro: printing is device-independent;
  • con: the CRD is not controllable;
• uploaded CRD:
  • pro: you can download the CRD you want;
  • con: printing is device-dependent.

Above illustrations are taken from Color Management Systems, an Adobe technical guide to ICC and PCM color management.