About Color Management Modules
A color management module (CMM) is a component that implements color matching, color gamut checking, and other services and performs these services in response to requests from ColorSync-supportive applications or device drivers.A CMM component interacts directly with the Component Manager, which calls the CMM on behalf of the ColorSync Manager and the requesting application or driver. When they call ColorSync Manager functions to request color-matching and color gamut-checking services, ColorSync-supportive applications and device drivers specify the profiles to use. These profiles characterize the devices involved; they include information giving the color spaces and the color gamuts of the devices and the preferred CMM to carry out the work. A CMM uses the information contained in these profiles to perform the processing required to service requests. Figure 5-1 shows the relationship between a ColorSync-supportive application or driver, the ColorSync Manager, the Component Manager, and a CMM.
A CMM should support all seven classes of profiles defined by the ICC. For information on the seven classes of profiles, see "Profile Classes" (page 3-13) in Advanced Color Imaging Reference, and the International Color Consortium Profile Format Specification, version 2.x. To obtain information from the ICC, visit the ICC Web site at the following location:
http://www.color.org/In some cases, a CMM will not be able to convert and match colors directly from the color space of one profile to that of another. Instead, it will need to convert colors to the device-independent color space specified by the profile. A CMM uses device-independent color spaces, or interchange color spaces, to interchange color data from the native color space of one device to the native color space of another device.The profile connection space field of a profile header specifies the interchange color space for that profile. Version 2.x of the ColorSync Manager supports two interchange color spaces: XYZ and Lab.Figure 5-1 The ColorSync Manager and the Component Manager
When interchange color spaces are involved, the ColorSync Manager handles the process, which is largely transparent to the CMM. The ColorSync Manager passes to the CMM the correct profiles for color matching. For example, in a case in which both the source and destination profile's CMMs are required to complete the color matching using color space profiles, the ColorSync Manager calls the source profile's CMM with the source profile and an interchange color space profile. Then it calls the destination profile's CMM with an interchange color space profile and the destination profile. The ColorSync Manager assesses the requirements and breaks the process down so that the correct CMM is called with the correct set of profiles. This process is described from the perspective of an application or device driver in "Developing ColorSync-Supportive Applications" (page 4-3).
A CMM uses lookup tables and algorithms for color matching, using one device to preview the color reproduction capabilities of another device, and checking for colors that cannot be reproduced.
