colour maps for the colour blind - peter kovesi · conclusions the colour maps are untested, but i...

Colour Maps for the Colour Blind

Peter Kovesi

Centre for Exploration TargetingSchool of Earth and Environment

The University of Western Australia

IAMG2017

protanopia

deuteranopia

tritanopia

Protanopia/Protanomaly: Red,Lconesmissing/reducedfunc=on. Red-Greenblind.1-2%males.

Deuteranopia/Deuteranomaly:Green,Mconesmissing/reducedfunc=on.

Red-Greenblind.6-8%males.Tritanopia/Tritanomaly: Blue,Sconesmissing/reducedfunc=on.

Blue-Yellowblind.Veryrare.

Testimageforcolourmaps:Asinewavesuperimposedonaramp

Agoodcolourmapwillrenderthesinewaveuniformlyacrosstheimage.

AmplitudeisreducedtozeroattheboMomoftheimage.

Amplitudeissetsothatpeaktotroughis10%ofthefulldatarange.

ColourMapRoadTest

Acolourmapisapaththroughcolourspace

LightnessdifferencesdominatesperceptualcontrastatfinespaCalscales.

Labcolourspace

TheColourMapDesignProcess

1)Defineacolourmappathusinglinesegmentsorsplines.

2)Ini=alcolourmap

3)Resamplecolourmappathatequallightnessstepstoobtainperceptualuniformity

PerceptuallyUniformColourMaps

VendorColourMaps Featuresdisappearatpointsoflowperceptualcontrast

Falsefeaturesthatareinthecolourmap,notinyourdata

tritanopia

protanopia

deuteranopia

Checkingtoseeifacolourmapis‘colourblindsafe’isnotopCmal

Colourmapdesignedsothatredandbluecoloursarematchedinlightnessandchroma.

Idealapproachistodesigncolourmapswithinthecolourspaceofthecolourblind

•  Ensuresmaximaluseofthecolourspace.

•  Allowseveryonetoshareacommonperceptualinterpreta=onofthedata.

•  Chromaandlightnesscanbeproperlyusedinthedesignofcolourmaps.

575nmisperceivedassameyellowbytrichromats,protanopesanddeuteranopes

Protananpic/DeuteranopicColourSpace

475nmisperceivedassamebluebytrichromats,protanopesanddeuteranopes

•  Assumethegreyscaleisperceivedinthesameway.

•  Usingdatafrompeoplewhoarecolourblindinjustoneeyeassumethefollowing:

575nmisperceivedassameyellowbytrichromats,protanopesanddeuteranopes

Protananpic/DeuteranopicColourSpace

475nmisperceivedassamebluebytrichromats,protanopesanddeuteranopes

•  Assumethegreyscaleisperceivedinthesameway.

•  Usingdatafrompeoplewhoarecolourblindinjustoneeyeassumethefollowing:

Protananpic/DeuteranopicColourSpaceinLMSconeresponsecoordinates

ColourspaceinLMSconeresponsecoordinates

HansBreMel,FrancoiseVienotandJohnD.Mollon.1997“Computerizedsimula=onofcolorappearancefordichromats”

(adistor=onoftheRGBcube)

Protanopicprojec=onofcoloursontocolourspace

Deuteranopicprojec=onofcoloursontocolourspace

Protananpic/DeuteranopicColourSpaceinCIELabcoordinates

Fullcolourspace

660nmisperceivedassameredbytrichromatsandtritanopes

TritanopicColourSpace

485nmisperceivedassameblue/greenbytrichromatsandtritanopes

TritanopicColourSpaceinLMSconeresponsecoordinates

Tritanopicprojec=onofcoloursontocolourspace

TritanopicColourSpaceinCIELabcoordinates

Fullcolourspace

Data:PropertyofFugroAirborneSurveysPtyLtdProcessing:PhasePreservingDynamicRangeCompression

divergingmaps

Conclusions

Thecolourmapsareuntested,butIproposethefollowing:•  Itisbesttodesigncolourmapswithinthecolourspaceofthe

colourblind,ratherthantestamapforcolourblind‘safeness’.

•  Workingwithinthecolourspaceofthecolourblindallowseveryonetoshareacommonperceptualinterpreta=onofthedata.

•  Ensuresmaximaluseoftheavailablecolourspace.

•  Chromaandlightnesscanbeproperlyusedinthedesignofcolourmaps.

Colourmapscanbedownloadedfrom:peterkovesi.com/projects/colourmaps