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Inside Macintosh: Advanced Color Imaging Reference /

Chapter 3 - ColorSync Manager Reference for Applications and Device Drivers / Constants and Data Types

ColorSync Flag Constants

Quality Flag Values for Version 2.x Profiles

The following enumeration defines the possible values for the quality bits in the flags field of the CM2Header structure. To determine the value of the quality flag, you mask the flags field of the profile header with the cmQualityMask mask, shift right 16 bits, then compare the result to the enumerated constants shown below. For more information on the quality flag, see "Flag Mask Definitions for Version 2.x Profiles" (page 3-29).

When you start a color-matching session, ColorSync sends all involved profiles to the color management module (CMM). The CMM extracts the information it needs from the profiles and stores an internal representation in private memory. The default CMM supplied by Apple Computer samples the input space and stores the results in a lookup table, a common technique that speeds up conversion for runtime applications. The size of the table is based on the quality flag setting in the source profile header. The setting of the quality flag can affect the memory requirements, accuracy, and speed of the color-matching session. In general, the higher the quality setting, the larger the lookup table, the more accurate the matching, and the slower the matching process. However, the default Apple CMM currently produces the same results for both normal and draft mode.

enum {
   cmNormalMode= 0,  /* use default method for quality */
   cmDraftMode = 1,  /* sacrifice quality to minimize resource
                        requirements */
   cmBestMode  = 2   /* ensure highest possible quality */
};

Enumerator descriptions

cmNormalMode

This is the default setting. Normal mode indicates that the CMM should use its default method to compromise between performance and resource requirements.

cmDraftMode

Draft mode indicates that the CMM should sacrifice quality, if necessary, to minimize resource requirements. The default Apple CMM currently produces the same results for both normal and draft mode.

cmBestMode

Best mode indicates that the CMM should maximize resource usage to ensure the highest possible quality.