Graphics Programs Reference
In-Depth Information
ation or error in reproducing my specific color from input to output is
1.6 deltaE. Changing the rendering intent updates all the calculations
showing how well the two profiles interact in reproducing this solid color.
When I selected the perceptual rendering intent, the new values were
calculated as 19/68/22 and the deltaE value dropped to 0.8.
Image Widgets
Although color reproduction calculation is useful for viewing how pro-
files affect solid colors and for providing numeric conversions of specific
values from source through destination, the real power of ColorPursuit
is in analyzing the actual profiles themselves using Image Widgets. There
are three different quality analyses available: Profile, Device, and Color
Reproduction.
ICC Profile Quality The first type of analysis is Profile Quality, which is
produced by calculating the errors found in the profile tables discussed
in Chapter 6. In this case, ColorPursuit produces conversions from the
AtoB and BtoA tables, something called the roundtrip , to produce a sta-
tistical quality analysis of the profile. That is, the analysis is based upon
both the device-to-PCS and PCS-to-device colorimetric and perceptual
tables. This gives a good overall indication of the profile quality. As seen
in Fig. 8-19, I've loaded a profile built for my Epson 2200. The average
deltaE error as well as the maximum deltaE for each of the tables is cal-
culated and shown in the Profile Quality info pane of the widget. The data
seen here is used to calculate the Profile QI (Quality Index). The smaller
the errors, the higher the Profile QI rating, which ranges from a scale of
1 to 10 with 10 being a prefect score (no errors).
Device Quality Notice that Fig. 8-19 shows an area in the feedback
window named Device Quality , the second type of profile analysis Color-
Pursuit can provide. Here ColorPursuit analyzes the attributes of the
device itself using the profile data. Physical Gamut is the analysis of the
profile's gamut based upon the colorimetric table. Expanded Gamut is
the analysis of the profile's gamut based upon the perceptual table. Device
QI (Quality Index) ranges from a scale of 1 to 10 with 10 being best
quality. The values provided indicate the percentage of colors that can be
reproduced on this device based upon the data calculated from the Profile
Quality data discussed earlier. Device Quality is primarily a measure of
the gamut of the device based upon the perceptual and colorimetric
tables, and can be useful for comparing two similar devices, such as two
different four-color presses or two different ink-jet printers. Having a
profile from each and analyzing the Device Quality can tell us which
printer has a wider gamut using a numeric scale, something a 3D gamut
map don't necessarily provide. In addition, we see the differences in both
the colorimetric versus the perceptual tables, again using a quality scale
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