an image basedmulti-angle measurement setup · an image basedmulti-angle measurement setup...
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An image based multi-angle measurementsetup
Aditya Sole
The Norwegian Colour and Visual Computing Laboratory, Norwegian University of Science and Technology
Gjøvik, [email protected]
http://www.ntnu.edu/colourlab
29th June, 2017
ICC Graphic Arts Experts’ Day, The Czech Academy of Sciences in Prague, June 29, 2017
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Introduction
Appearanceofanobjectmaterial
sparadvertising.com
www.beautypackaging.co
m
WhatColor?Glossy/matte?Texture?Opaque/translucent?
MaterialAppearance
2
Introduction
Appearanceofanobjectmaterial
sparadvertising.com
www.beautypackaging.co
m
WhatColor?Glossy/matte?Texture?Opaque/translucent?
MaterialAppearance
Objectivedescription
Surfacereflectance,Specularmeasurement,texturepatterns,Opacity,etc.
PhysicalMeasurements
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4
Non-diffuse, gonio-chromatic materials
www.scrangie.com
• Usedinpackagingindustry,carpaintindustry,banknotesetc.• Createdusing,
• Metallicinks,• Pearlescent,varnishcoatings,• Specialeffectpigments,• Holographicfoils.
• Producedesirableappearancebyshift/changeinperceivedcolour dependinguponillumination/viewinggeometry.
• Changeduetovaryingreflectionatdifferentviewingangles(basedonmaterialproperties).
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• Multi-anglemeasurementinstrumentsavailableinthemarket,
• X-RiteMA98,BYC-MAC,etc,• Gonio-reflectometers atmetrology
institutes.
GONIO-MEASUREMENTS / MULTI-ANGLE MEASUREMENTS
Images taken from:K. Kehren, Optical Properties and Visual Appearance of Printed Special Effect Colors, PhD thesis, Technischen Universität Darmstadt, Darmstadt, Germany, April 2013.
Licensed under CC BY-NC-ND
Limitations:• Measurementsaretimeconsuming
(especiallyGonio-reflectometers),• Expensive.
6
Motivation
• Canweperformmulti-anglemeasurementsinafastandrelativelyin-expensiveway?
• Canthemeasurementsbedoneonlineduringthereproductionand/orimagequalityevaluationproceduresintheproductionline?
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Image based multi-angle measurement setup1,2
• Animage-basedmulti-anglemethodformeasurementofhomogeneousflexibleobjectmaterial
• UsingpointlightsourceandaRGBcamera,
• Estimatetheincident(θi) andreflection(θr) anglesofacurvedsample.
cosθi =PL ⋅nPL
cosθr =PC ⋅nPC
dL
(dC))(
d
θLθS
θiθr (n)(P)
Camera
Light source
1. A.Sole;I.Farup;S.Tominaga,“Animage-basedmulti-directionalreflectancemeasurementsetupforflexibleobjects”,Proc.SPIE9398,Measuring,Modeling,andReproductionMaterialAppearance2015,93980J(March13,2015)
2. A.Sole,IFarup,STominaga,(2014)Animagebasedmulti-anglemethodforestimatingreflectiongeometriesofflexibleobjects,Proc.IS&T/SID22ndColorImagingConference,Boston,Arizona,USA,91-96.
8
Image based multi-angle measurement setup1,2
dL
(dC))(
d
θLθS
θiθr (n)(P)
Camera
Light source
1. A.Sole;I.Farup;S.Tominaga,“Animage-basedmulti-directionalreflectancemeasurementsetupforflexibleobjects”,Proc.SPIE9398,Measuring,Modeling,andReproductionMaterialAppearance2015,93980J(March13,2015)
2. A.Sole,IFarup,STominaga,(2014)Animagebasedmulti-anglemethodforestimatingreflectiongeometriesofflexibleobjects,Proc.IS&T/SID22ndColorImagingConference,Boston,Arizona,USA,91-96.
9
Image based multi-angle measurement setup1,2
dL
(dC))(
d
θLθS
θi
θr(n)(P)Camera
Light source
1. A.Sole;I.Farup;S.Tominaga,“Animage-basedmulti-directionalreflectancemeasurementsetupforflexibleobjects”,Proc.SPIE9398,Measuring,Modeling,andReproductionMaterialAppearance2015,93980J(March13,2015)
2. A.Sole,IFarup,STominaga,(2014)Animagebasedmulti-anglemethodforestimatingreflectiongeometriesofflexibleobjects,Proc.IS&T/SID22ndColorImagingConference,Boston,Arizona,USA,91-96.
10
Image based multi-angle measurement setup1,2
dL
(dC))(
d
θL θS
θi
θr
(n)
(P)
Camera
Light source
1. A.Sole;I.Farup;S.Tominaga,“Animage-basedmulti-directionalreflectancemeasurementsetupforflexibleobjects”,Proc.SPIE9398,Measuring,Modeling,andReproductionMaterialAppearance2015,93980J(March13,2015)
2. A.Sole,IFarup,STominaga,(2014)Animagebasedmulti-anglemethodforestimatingreflectiongeometriesofflexibleobjects,Proc.IS&T/SID22ndColorImagingConference,Boston,Arizona,USA,91-96.
11
Sample measurement• Assumingmeasurementsample
tobehomogeneousandopaquewemeasurewith:
• 10illuminationdirections,• Spectralon tileasreference
tiletoestimatelinearRGBcameraresponseoftheincidentlight,
• NikonD200DSLRcamera,• Tungstenpointlightsource,• Printedpackagingsheetas
sample
A.Sole,I.Farup,andP.Nussbaum,“Evaluatinganimagebasedmulti-anglemeasurementsetupusingdifferentreflectionmodels”,inMaterialAppearance,vol.2017,no.8,pp.101-107,ProceedingsIS&TElectronicImaging,2017
Munsell White
Red
Cyan
Pantone 10309C
Magenta
Pantone 10213C
Pantone 10153C
Spectralon tile
12
Surface reflectance using a reflection model• Forexample:
• Phong reflectionPhong reflectionmodelisanempiricalmodelwithtwosurfacereflectioncomponents,diffusereflectionofroughsurfacesandspecularreflectionofshinysurfaces
• Cook-TorrancemodelCTmodelisaphysicalmodelthatdescribestheintensityandspectralcompositionofthelightreflectedfromtheobject/material.
• IsotropicWardmodelWardmodelisaphenomenologicalmodeldevelopedwiththeaimtofitmeasuredreflectancedatawithasimpleempiricalformula.Itrepresentsbothisotropicandanisotropicreflectionand usesagaussian distributionforthespecularpeaks.
Comparing with Gonio/Multiangle spectrophotometers
Image taken from:K. Kehren, Optical Properties and Visual Appearance of Printed Special Effect Colors, PhD thesis, Technischen Universität Darmstadt, Darmstadt, Germany, April 2013.
Licensed under CC BY-NC-ND
CameraSetup– RGB Multi-angle/GoniospectrophotometerSetup– Spectral400– 700nm
Image taken from:http://www.ebay.com/gds/Nikon-D200-Vs-Nikon-D-Series-D300-
/10000000177709780/g.html
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CameraMeasurement
RGB
Multi-angle/Goniospectrophotometer
Spectralreflectance400nm........700nm
XYZ=XYZreflectance,RGB=Illuminantindependentcameraresponseofthesamplematerial,
XYZ
𝑋 =#𝐶𝑟 𝜆 𝑅𝑒(𝜆)+,,
-,,
𝑌 =#𝐶𝑔 𝜆 𝑅𝑒(𝜆)+,,
-,,
𝑍 =#𝐶𝑏 𝜆 𝑅𝑒(𝜆)+,,
-,,
XYZRe(𝜆)=spectralreflectance,𝑪3(𝑪𝒓 𝝀 𝑪𝒈 𝝀 𝑪𝒃 𝝀 )=transformedcolour matchingfunctionsusingcamerasensitivityfunctionsand2○ (�̅�,𝑦<,𝑧̅)colour matchingfunctions.
∎ ∎ ∎∎ ∎ ∎∎ ∎ ∎
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Comparing with Gonio-spectrophotometers
𝑀3
Transformation Matrix (𝑀3) and transformed colourmatching functions (𝐶@)
𝑀3 = 𝑎𝑟𝑔minE
𝐶 − 𝑅𝑀 G
C=31x3matrix(CIE2○ colour matchingfunctions),
R=31x3matrix(camerasensitivityfunctions(𝑟 𝜆 , 𝑔(𝜆),b(𝜆)),
𝑀3=3x3transformationmatrix,
𝐶@=31x3matrix(transformedcolour matchingfunctions),
𝐶@ = 𝑅𝑀3
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A.Sole,I.Farup,andS.Tominaga,“Imagebasedreflectancemeasurementbasedoncameraspectralsensitivities,”inMeasuring,ModelingandReproducingMaterialAppearance2016(M.V.O.Segovia,P.Urban,andF.H.Imai,eds.),vol.2016,no.9,pp.1– 8,Proceedings IS&TElectronicImaging,2016.
XYZ_Y value of Cyan sample
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Munsell White
Red
Cyan
Pantone 10309C
Magenta
Pantone 10213C
Pantone 10153C
Spectralon tile
Sample
A.Sole,I.Farup,andP.Nussbaum,“Evaluatinganimagebasedmulti-anglemeasurementsetupusingdifferentreflectionmodels”,inMaterialAppearance,vol.2017,no.8,pp.101-107,ProceedingsIS&TElectronicImaging,2017
17
• Measurement data divided into training and test data set
• Training set: 5°, 15°, 20°, 25°
and 30°
• Training of Cook-Torrance and Isotropic Ward model
Training of the reflection models
A.Sole,I.Farup,andP.Nussbaum,“Evaluatinganimagebasedmulti-anglemeasurementsetupusingdifferentreflectionmodels”,inMaterialAppearance,vol.2017,no.8,pp.101-107,ProceedingsIS&TElectronicImaging,2017
18
Cyan sample𝐻𝑖𝑠𝑡𝑜𝑔𝑟𝑎𝑚𝐶𝑦𝑎𝑛𝑆𝑎𝑚𝑝𝑙𝑒𝐶𝑇𝑎𝑛𝑑𝑊𝑎𝑟𝑑𝑚𝑜𝑑𝑒𝑙
ResultMunsell White
Red
Cyan
Pantone 10309C
Magenta
Pantone 10213C
Pantone 10153C
Spectralon tile
• CYANsamplemeasuredusingtele-spectro-radiometerØ 𝐼𝑛𝑐𝑖𝑑𝑒𝑛𝑡𝑑𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛(𝜃Y) = 40°, 𝑉𝑖𝑒𝑤𝑖𝑛𝑔𝑑𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛𝑠(𝜃_) = −10°, 0°, 10°, 𝑎𝑛𝑑30°
• TrainedCTandWardmodelsusedtoestimatetheCIEYvalueatthesesameincidentandviewingdirections
Physical measurements using radiometer
CYANsample
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• For the sample materials used in this paper
Ø Satisfactory performance of both the reflections models for the given set of sample materials
Ø Directionalreflectionpropertiesofthematerialcanbeestimateddirectlyinthecolorimetricspace,
Ø Ward model estimates CIE Y values well for the measurements made with the tele-spectro-radiometer
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Conclusion
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Future work
• To evaluate the setup, perform sample measurements with the setup and compare with gonio-spectrophotometer measurements.
• Implement the method on highly specular and gonio-chromatic samples.
• Use the setup to measure specular materials along with more complex BRDF reflection models.
Thank you foryour attention
Contact information:AdityaS.SoleE-mail:[email protected]:www.ntnu.edu/colourlab