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