Three-Dimensional Control of Color Management Systems - Control of Color Imaging Systems: Analysis and Design - page 411

FIGURE 7.68 (See color insert following page 428.) Example of out-of-gamut color
sweeps — susceptible to contours (see Figure 7.40 for performance with MM algorithm vs. the
control-based inversion).

7.8 AN EXAMPLE SHOWING HOW TO BUILD
MULTIDIMENSIONAL INVERSE LUT
The ICC pro le architecture assumes a reference color space in L*a*b*orXYZ

values (called PCS) for standard observers, measurement geometry, and number
of illuminants. For this example to build an ICC pro le for a printing device with

media relative colorimetric rendering intent, let us restrict the colorimetric options
to a 2 degree observer, and a D50 illuminant source with the PCS de

ned by L*a*b*
values. We adopt relative-to-paper colorimetry to incorporate a standard reference
media to reduce paper dependency. That is, the paper white will have the PCS
values of {100, 0, 0}. All re ectance measurements are done with a speci ed

measurement geometry (0 les with other rendering intents

(e.g., perceptual, saturation etc.) can also be easily built by incorporating proper tone
scale adjustments, compression, and other compromises to the basic colorimetric
pro

= 45 or 45 = 0). The ICC pro

le.
A 3DLUT is a major component of the destination ICC pro le which is a GCR-

constrained, gamut-mapped transformation LUT from RGB triplets to device CMYK
space. Hence we

first show the detailed steps involved in building the 3DLUT
starting from a printer model. We use the footprint shown in Figure 7.1 to describe
the steps. For convenience, we use a low resolution LUT of size 6 3 to show the
numerical values. The performance is evaluated for a high resolution 33 3 LUT using
the same printer model.
Step 1: Choose a working color space for RGB triplets. There are numerous choices
for this (Adobe RGB, Apple RGB, CIE RGB, ColorMatch RGB, NTSC RGB, Wide