an interactive perception based model for characterization of display devices 1 institute of...
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An Interactive Perception Based An Interactive Perception Based Model for Characterization of Model for Characterization of
Display DevicesDisplay Devices
11 Institute of Computer Graphics and Algorithms Institute of Computer Graphics and AlgorithmsVienna University of Technology, AustriaVienna University of Technology, Austria
22 Grup de GrGrup de Grààfics de Girona, fics de Girona, Universitat de Girona, SpainUniversitat de Girona, Spain
Attila NeumannAttila Neumann11, Alessandro Artusi, Alessandro Artusi11, ,
Georg ZottiGeorg Zotti11, L, László Neumannászló Neumann22, ,
Werner PurgathoferWerner Purgathofer11
Attila Neumann Computergraphik @ TU Wien
MotivationMotivation
By human observation
Reliable characterization of display
By a measuring device
Attila Neumann Computergraphik @ TU Wien
Colors of the displayColors of the display Additive RGB channelsAdditive RGB channels
characteristics separable by channelcharacteristics separable by channel Side effectsSide effects
slight cross effects (stronger for LCD)slight cross effects (stronger for LCD) environmental effectsenvironmental effects
PipelinePipeline graphics card [byte]graphics card [byte] display device [voltage]display device [voltage] eye [luminance]eye [luminance] brain [color appearance]brain [color appearance]
Attila Neumann Computergraphik @ TU Wien
Tone Reproduction CurveTone Reproduction Curve
byte → luminance (by channel)
Attila Neumann Computergraphik @ TU Wien
Previous Work – Models for the TRCPrevious Work – Models for the TRC Models with small number of parametersModels with small number of parameters
Linear functions: Linear functions: GOG, version 1.x IEC GGO, version 2.x 3.x IEC GOGO GOG, version 1.x IEC GGO, version 2.x 3.x IEC GOGO [Berns et al. 1993][Berns et al. 1993]
Non linear functions: Non linear functions: LIN-LIN2, LOG-LIN, LOG-LIN2, LOG-LOG, LOG-LOG2 LIN-LIN2, LOG-LIN, LOG-LIN2, LOG-LOG, LOG-LOG2 [Post and Calhoun 1989], [Katoh and Deguchi 1998][Post and Calhoun 1989], [Katoh and Deguchi 1998]
S-curve (S-shaped function): S-curve (S-shaped function): handling cross effect (mainly at LCD monitors)handling cross effect (mainly at LCD monitors) [Kwak MacDonald 2001], [Miyake et al. 1990][Kwak MacDonald 2001], [Miyake et al. 1990]
Arbitrary number of parametersArbitrary number of parameters Masking model Masking model (spline)(spline)
[Tamura et al. 2003] [Tamura et al. 2003]
Attila Neumann Computergraphik @ TU Wien
Our methodOur method
Basic measurement stepsBasic measurement steps Human observationsHuman observations
Errors are tolerable and can be reducedErrors are tolerable and can be reduced Relative measurementsRelative measurements
Finding the input values (instead of output values) Finding the input values (instead of output values) Automatic stop and setup of basic stepsAutomatic stop and setup of basic steps
Optimization (definition of the TRC function)Optimization (definition of the TRC function)
Generic function is achievedGeneric function is achieved A relative curve is definedA relative curve is defined Passes requirements of human perceptionPasses requirements of human perception
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Similar to classic gamma applet
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Attila Neumann Computergraphik @ TU Wien
Basic step Basic step
Attila Neumann Computergraphik @ TU Wien
The math problemThe math problem No direct measurements for No direct measurements for f(x)f(x)
onlyonly relative measurements relative measurements ((x((x00, x, x22, r), , r), xx11))
diff = ydiff = y11‘-y‘-y1 1 = r= rf(xf(x00)+(1-r))+(1-r)f(xf(x22)-f(x)-f(x11))
depends on the depends on the unknownunknown y=f(x)y=f(x) TRC TRC
Optimum criteria Optimum criteria for the for the y=f(x)y=f(x) TRC TRC y‘-yy‘-y expressions are to be expressions are to be minimizedminimized
instead of the usual instead of the usual yyii=f(x=f(xii)) i.e. i.e. diffdiffii=0 =0 !!!! other targets can be definedother targets can be defined
smoothness conditionsmoothness condition repeatable measurementsrepeatable measurements
Attila Neumann Computergraphik @ TU Wien
The compound minimum problemThe compound minimum problemf(i) [i=0..255] f(i) [i=0..255] are unknownare unknown
Measurement conditions:Measurement conditions:
M(j) = rM(j) = rjjf(lowf(lowjj)+(1-r)+(1-rjj))f(highf(highjj)-f(back)-f(backjj) ) [j=1..N] [j=1..N]
Smoothness conditions:Smoothness conditions:S(i) = f(i+1)+f(i-1)-2S(i) = f(i+1)+f(i-1)-2f(i) f(i) [i=1..254] [i=1..254]
Convex quadratic minimum problemConvex quadratic minimum problem
F = F = i=1..Ni=1..N m mjjM(j)M(j)22 + + i=1..254i=1..254 s siiS(i)S(i)22
Minimized by a conjugate gradient methodMinimized by a conjugate gradient method
Attila Neumann Computergraphik @ TU Wien
Additional questionsAdditional questions Setting the coefficientsSetting the coefficients
weightsweights m m and and ss control the behaviour of control the behaviour of ff Definition of triplets Definition of triplets (low(lowii, high, highii, ratio, ratioii))
predefined tripletspredefined triplets optimal ‚next triplet‘, stop criteriumoptimal ‚next triplet‘, stop criterium
defined by the local and/or overall defined by the local and/or overall reliabilityreliability LOG-LOG coordinate systemLOG-LOG coordinate system
Seems more naturalSeems more natural power function transformed to linear functionpower function transformed to linear function
Additional degree of freedomAdditional degree of freedom But: numerical and algorithmic problemsBut: numerical and algorithmic problems
Attila Neumann Computergraphik @ TU Wien
ResultsResults CRT monitorCRT monitor
R,G,B results R,G,B results byby our method our method
Compared to Compared to simple power simple power functionfunction
Perceivable Perceivable deviationdeviation
Derivative can deviate upto 0.4-0.6 !
Attila Neumann Computergraphik @ TU Wien
ResultsResults Compared to Compared to
spectro-spectro-photometer photometer measurementsmeasurements
Absolute/relative Absolute/relative data conversiondata conversion
Accuracy Accuracy acceptableacceptable
Mutual Mutual verificationverification
Attila Neumann Computergraphik @ TU Wien
Conclusion, future workConclusion, future work+ + Human based TRC measurementHuman based TRC measurement
Cheap solutionCheap solution New implicit approachNew implicit approach
+ + Complements existing methodsComplements existing methods Traditional gamma appletTraditional gamma applet Masking model [Tamura 2003]Masking model [Tamura 2003]
? ? Missing absolute luminance valuesMissing absolute luminance values By channel, cross effectsBy channel, cross effects
contrast value by human observationcontrast value by human observation
? ? Preferring LOG-LOG type functionsPreferring LOG-LOG type functions Instead of spline-like (LIN-LIN) functionsInstead of spline-like (LIN-LIN) functions
? ? Combining with other methods (LIN-LIN, etc)Combining with other methods (LIN-LIN, etc)
Attila Neumann Computergraphik @ TU Wien
AcknowledgementsAcknowledgements Supported bySupported by
European Union: RealReflect ProjectEuropean Union: RealReflect Project IST-2001-34744 IST-2001-34744 „„Realtime Visualization of Complex Behaviour Realtime Visualization of Complex Behaviour
in Virtual Prototyping“in Virtual Prototyping“ Spanish GovernmentSpanish Government
TIC2001-2416-C03-01TIC2001-2416-C03-01
Helped with implementationHelped with implementation Benjamin Roch (TU Vienna, Austria)Benjamin Roch (TU Vienna, Austria) Wolfgang Deix (TU Vienna, Austria)Wolfgang Deix (TU Vienna, Austria)
Attila Neumann Computergraphik @ TU Wien
Thank you Thank you for your attentionfor your attention