Date post: | 22-Jan-2018 |
Category: |
Engineering |
Upload: | jan-morovic |
View: | 176 times |
Download: | 1 times |
© Copyright 2017 HP Inc.
HANS Print Smoothness Optimization and Continuous Control
Ján Morovič & Peter MorovičHP Inc., Barcelona, Catalonia, Spain
Presented at CIC 25, 14 September 2017, Lillehammer, Norway
© Copyright 2017 HP Inc.
Outline
• Once upon a time in New Mexico
• HANS basics
• Optimizing for smoothness
• Results
• Summary
© Copyright 2017 HP Inc.
“Is the set of all possible spectra convex?”
Albuquerque, NM 10th November 2007
Once upon a time in New Mexico
© Copyright 2017 HP Inc.
From Maxwell to “print-well”
© Copyright 2017 HP Inc.
“What would happen if we controlled the Neugebauer Primary at each halftone pixel,
instead of only ink amounts?”
© Copyright 2017 HP Inc.
MuchMuch more choice
Alternative basic NPacs:
6086(in 34=81D)
Alternative basic ink combinations:2(in 4D)
C=34%M=27%Y=28%
C=7%Y=1%K=27%
W=77%C1=1%Y1=2%K1=20%
W=79%Y1=2%K1=14%Y1K1=2%C2=1%K2=2%
W=70%C1=2%M1=5%Y1=5%K1=6%C1M1=1%C1K1=2%M1K1=3%Y1K1=2%C2=4%
Print color
3000x possible
patterns (same color)
included
Full gamut choices
Ink space: 2.8 x 1014
HANS:1.5 x 10172
Better ink efficiency & color gamut (CIC18, NIP ’11, IEEE TIP ’11)
CMY metamers (CIC19)
Spectral printing (CIC20)
8-vertex pipeline (CIC21)
Color & spectral print preview (CIC23)
Large gamut and spectral display (CIC24, JOSA A ’16)
Single-matrix halftoning (CIC24, IEEE TIP ’17)
Print smoothness (CIC25)… one more thing → HANS X (CIC25)
Ink-vectors NPacsD # D #
CMY 1dpp 8bit 3 107 8 1014
CMYK 2dpp 8bit 4 109 81 1079
CMYK 2dpp 12bit 4 1014 81 10172
Atoms in universe 1078-1082
© Copyright 2017 HP Inc.
Optimizing for smoothness:An engineering approach
• How do I find the patterns that result in the smoothest prints? • Define smoothness metric
• Needs to be fast (applied to millions of patterns)
• Enough if it is monotonic with perceived smoothness ← pick smoothest from among set
• Generate loads of pattern statistics (NPacs) & group by color
• Evaluate metamer set members
• Select smoothest pattern for each color
• Build look-up table from smoothest patterns
© Copyright 2017 HP Inc.
16 color patches (NPacs + printed)
A simple print smoothness metric
lowgrain
mediumgrain
highgrain
6 observers
perceived smoothness
digital halftones (predicted color at pixel)
metrics (σ-based, w/ or w/o CSF, w/ or w/o YN)
predicted smoothness
reorder for prediction
originalsimplestbest
© Copyright 2017 HP Inc.
Smoothness optimization• Find smoothest patterns spanning the available
color gamut: • Generate NPacs using RANSAC, • Predict colorimetry & smoothness, • Subdivide color space into bins (paramer
sets), assign NPacs to bins, • For each bin, select NPac with highest
smoothness score • Printing system: CMYK on HP Heavyweight
Coated paper, w/ up to two drops per ink per halftone pixel → 3^4=81 NPs
• Color model: RONT model (CIC23) w/ mean of 0.9, 95th perc. of 2.2 and max. of 3.4 ∆E2000
• Bins: 25^3 • NPacs generated, evaluated and binned:
13 171 174 • Result: 1257 non-empty bins
NPacs with (top) lowest and (bottom) highest grain. NPac markers shows color and size indicates grain. Black lines
connect the NPacs to centroid of bin containing it.
© Copyright 2017 HP Inc.
Results
highest smoothness
lowest smoothness
© Copyright 2017 HP Inc.
One more thing: continuous control
LUT with highest smoothness (Higher cost)
LUT with lowest smoothness (Lower cost)
w 1-w
© Copyright 2017 HP Inc.
Summary
10th anniversary of HANS(born at CIC 15)
Pixel content control instead of colorant control opens up new possibilities
Simple, engineering approach to smoothness optimization delivers strong results
HANS domain enables continuous control 🎂
© Copyright 2017 HP Inc.
Acknowledgements
• Africa Real
• Albert Serra
• Annarosa Multari
• Hector Gomez
• Joan Enric García
• Joan Manel García Reyero
• Jordi Arnabat
• Martí Rius
• Pere Gasparin
• Victor Diego
• Xavi Fariña