While there may be no point in arguing about taste, creative professionals make a living from sharing theirs. Making specific, individual color preferences that a creative professional knows how to achieve when creating content on a display also propagate into print is a significant challenge since it lacks real-time feedback. The present paper introduces a method for allowing creative professionals to use the tools they know and love to also personalize the color behavior of their devices. This is achieved by analyzing color changes applied to images and applying them to a device’s ICC profile. As a result the personalized device results in customized color behavior regardless of the workflow used. The paper describes the ICC profile transformation algorithm in detail and provides a color error analysis of its performance.

1. Natural Colour Profile
Adjustment for Professionals
Peter Morovič, Ján Morovič, Jordi Arnabat, Jordi Vilar, Angel Albarrán
Hewlett Packard Company
Barcelona, Spain
Kindly presented by Hila Nachlieli of HP Labs, Israel
The 6th European Conference on Colour in Graphics,Imaging and Vision
May 2012, Amsterdam (The Netherlands)

2. Understanding Artists
• Today’s devices are more repeatable, more consistent
and more accurate than ever before
… they are also less personal
• Photographers, designers, artists want to have a
personal look & feel in all embodiments of their art
(screen, print, ...)
• Artists care a lot about their art:
“Sometimes I have not even recognised my own
photographs. I have even hesitated to call them my G. Pinkhassov
own. […] Whoever controls the editing of a
photographer, controls his fate.” G. Pinkhassov/Magnum
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3. Tuning a device (printer)
• Calibration: consistent, repeatable output repeatable
• All devices produce skin tones of the same mine?
green hue, neutrals are consistently red
• Profiling: accuracy
• Skin tones print as skin-tones and
neutrals are neutral
• What about my preference? accurate
[the missing part]
mine?
• I like my skin-tones to be warmer
• I like my neutrals to be bluish
• I like slightly higher contrast
• ...and I want it systematically
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4. Learn my preference
Consistent
Accurate
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5. Learn my preference
Consistent
Accurate
Mine
5 /15

6. From image to print
ICC profile transformation sequence in a printing pipeline:
most photographers use it (and trust it) to get best results
sRGB preview of image
sRGB image
in output profile
sRGB Printer
ICC Profile ICC Profile
sRGB LAB dRGB
sRGB.icc Printer/Media.icc
Q1: how can we modify this workflow?
Q2: how can an artist easily “teach” the workflow it’s preference?
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7. Image based workflow
elect Image Select Image
1
Adjust all
Adjust only
images one
one image
by one
in Photoshop Adjust in Photoshop
2
NO (4) NO (4)
iterative iterative
justments adjustments
3 Satisfied? Print 3 Satisfied?
YES (4) YES (4)
w ICC Profile Save copy of
computed Next Image image incl print
d registered adjustments
As many
A single file files as
is created images/
media
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8. ICC based workflow
Select Image Select Image
1 1
Adjust only
one image
Adjust in Photoshop Adjust in Photoshop
2 2
NO (4)
iterative iterative
adjustments adjustments
Print 3 Satisfied? Print 3
YES (4) YES (4)
New ICC Profile Save copy of
is computed Next Image image incl print
and registered adjustments
A single file
is created
8 /15

9. ICC mechanics
• The ICC profile uses a series of sRGB
mechanisms to map to/from device
space to/from colorimetry (the PCS),
such as: LAB
sRGB ICC
Profile
- 1D linearisation tables
- ND Colour Look-Up Tables Desired
CLUT
- 3x3 transforms (for XYZ PCS) Color
Adjustment Reference
dRGB
ICC Profile
• Given the “before” and “after” images
adjusted by photographer: CLUT'
• A pixel-by-pixel and colour-by-colour dRGB'
New ICC
analysis let’s us devise a new ICC profile Profile
that embodies the desired adjustment
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10. Algorithm
• Introduced adjustment shifts Unadjusted Adjusted
expressed in PCS (CIE LAB) – a sRGB dRGB
perceptually near-uniform space
AToB AToB & BToA
• Uses same interpolation as CMM LAB dRGB
• Importance of shift is weighted by
number of pixels changed – average in 1D LUT (out 1D LUT)-1 (out 1D LUT)-1
shift encoded LAB' dRGBCLUT dRGB'CLUT
• Can represent some spatial editing
• Image-gamut relative colour Weights Shifts
adjustments ϖ δ
• Post-algorithm LUT smoothing is
applied Weighted shifts
Δ = Σ(δϖ)/Σ(ϖ)
• Fast – image is parsed only once
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11. Scope
• Systematic adjustment
• Makes sense if there is a systematic adjustment that is desired by
a user – not if each image requires a different change
• Does not replace retouching
• Spatial changes will be taken into account on average (e.g. if the
blues of a sky are modified but the blue of the sea is not, an average
will be considered)
• Global-local choice
• Colour–global adjustments applied to image with native gamut
should remain local to image gamut or not?
• Designed for fine-tuning
• Assumes a calibrated, profiled device on top of which fine
adjustments are introduced. Can work to compensate small
shortcomings/trade-offs of profiling engines too.
11 /15

12. Results – Qualitative
adjusted by algorithmic
• Environment: Calibrated monitor (EIZO), unadjusted
photographer processing
Photoshop CS4, Calibrated and Profiled HP
Z3100 (ICC also used for soft-proofing),
VeriVide viewing booth with D50 for
viewing prints
• 24 sets of [photo/substrate] adjustments
by 12 pro-photo/fine artists using full
Photoshop functionality (USA, Spain, UK) –
after adjustment, new ICC computed and
applied:
• asked to compare
[adjusted image + reference profile] vs
[unadjusted image + computed profile]
• no difference was reported
• asked to apply computed profile to other
images from “a set”
• adjustments were as expected
unadjusted algorithmic processing
12/15

13. Results – Quantitative
• Compare pixel–by–pixel CIE DE 2000 5
between: 4.5
[adjusted image + reference profile] vs
[unadjusted image + computed profile]
4
3.5
• Median always below 0.5 DE00 – 3
blue circles
CIE DE2000
2.5
• 95th %tile always below 2.5 DE00 2
(below 1 DE00 for all but one case) 1.5
– red circles 1
• Reference values: 2.5 DE00 noticeable 0.5
– 5 DE00 objectionable in complex 0
1 2 3 4 5 6 7 8 9 10 11 12 1 14 15 16 17 18 19 20 21 22 23 24
photographic content
Image Adjustment Number
13 /15

14. Summary
• colour preference algorithm shown to
work well for ‘small tweaks’ (on top of
calibration and profiling)
• uses using existing ICC mechanisms
(results in a standard ICC profile)
• fits seamlessly in existing workflow
(known tools to make adjustment,
simplified workflow when printing)
• demonstrated on printers – applies
equally to projectors/displays/...
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15. G. Pinkhassov – Magnum
Dank u wel!