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The ColorSync Manager defines the structure
CM2Header
to represent the profile header for the version 2.x profile format defined by the ICC. The
renderingIntent
field of the
CM2Header
structure is an unsigned long value whose bits specify information about a profile. The ICC reserves the use of bits 0 to 15 and has assigned values to bits 0 and 1. Bits 16 to 31 are reserved for use by color management system (CMS) vendors.
Figure 5-3
shows the bit assignments of the
renderingIntent
field specified by the ICC.
Rendering intent controls the approach a CMM uses to translate the colors of an image to the color gamut of a destination device. Your application can set a profile's rendering intent, for example, based on a user's choice of the preferred approach for rendering an image.
Figure 5-3 The renderingIntent field of the CM2Header structure
The following enumeration defines the four possible values for the rendering intent bits of the renderingIntent field. Because rendering intent is specified by the low two bits, and because no other bits are currently defined for this field, you can use the constants defined here to test or set the value of the entire field, without concern for possible information stored in other bits.
enum {
cmPerceptual = 0, /* scale colors to fit in gamut */
cmRelativeColorimetric = 1, /* don't change colors that fall in
the gamuts of both devices */
cmSaturation = 2, /* maintain relative saturation */
cmAbsoluteColorimetric = 3 /* base on idealized, device-
independent color space */
};