Colormaps for linear visual perception AND grayscale printing

Question

There are already good approaches for "better than standard" colormaps in Mathematica, which are optimized for a more linear perception between the visible colors and their underlying values, here in StackExchange: Is there an easy way to use Matteo Niccoli's perceptual color maps for 2D plots in Mathematica?

Nevertheless, those considerations can go even further into thinking of colormaps that also include linear perception for persons impaired by deuteranopia or protanopia. Also the grayscale-printing can be optimized.

Have a look at this page.

Example:

Question:

Far down in the article, there are some hints to generate those maps using Python. How can those maps be generated and used in Mathematica? I am particularly interested in "Option D (Viridis)".

What I have tried/found out so far:

On the article's website, I found a Python script including a variable cm_data, which contains apparently RGB values (scaled from 0.0 to 1.0) in a structure like: [[R1,G1,B1],...,[Rn,Bn,Gn]]. I'm not familiar with parsing such a string into a useful List in Mathematica.

You can think of some ways to programmatically parse cm_data, but why not just open a text editor or even MA for that matter and replace [ with { and so on. You will get a Listwhich is perfectly valid MA construction. — yarchik, Commented Sep 27, 2016 at 9:21
Well, I'm kind of embarrassed by the disarming simplicity of your idea. It is completely acceptable, and I'm going to do it like this. — DPF, Commented Sep 27, 2016 at 9:31
FYI: I don't know about others, but the answer I provided on the question you linked to reduces to grayscale appropriately. I believe it should also work for various types of colorblindness since the data is actually coded in the intensity, though using different parameters for differentiation between plots would require more consideration. — N.J.Evans, Commented Sep 27, 2016 at 13:26

Community · Accepted Answer · 2017-04-13 12:56:06Z

Didn't see george's answer when I worked this out, but I'll go ahead and post since it has all the maps from that page. The StringReplace here is pretty embarrassing, but I was going for quick and dirty

ClearAll@MPLColorMap
Set[
 Evaluate[
  MPLColorMap /@
   {"Magma", "Inferno", "Plasma", "Viridis", 
    "EricsRdBuGnYl", "EricsRdBuGnYl2", "EricsPuBuGnYl", "FakeParula", 
    "JoesBluGrnPnk2"}
  ],
 Function[url,
   ReadList[url, "String"][[
        Span[#1, #2 - 1] & @@ (Flatten@Position[
            StringPosition[test, "cm_data", IgnoreCase -> True],
            Except@{}, 1, Heads -> False])]] //
      StringReplace[
       {"[[" -> "{", "]]" -> "}", "]," -> "}", "[" -> "{", "]" -> "}",
         "cm_data = " -> "", "e" -> "*^"}
       ] // Map@RGBColor@*ToExpression // 
    Function[x, Blend[#, x]] &] /@ {
"https://raw.githubusercontent.com/BIDS/colormap/master/option_a.py",
"https://raw.githubusercontent.com/BIDS/colormap/master/option_b.py",
"https://raw.githubusercontent.com/BIDS/colormap/master/option_c.py",
"https://raw.githubusercontent.com/BIDS/colormap/master/option_d.py",
"https://github.com/BIDS/colormap/raw/master/erics-RdBuGnYl_r.py",
"https://github.com/BIDS/colormap/raw/master/erics-RdBuGnYl_r_v2.py",
"https://github.com/BIDS/colormap/raw/master/erics_PuBuGnYl_r.py",
"https://github.com/BIDS/colormap/raw/master/fake_parula.py",
"https://github.com/BIDS/colormap/raw/master/joes-blu_grn_pnk2.py"}
]

You can skip that code above and just import the data using

ClearAll[MPLColorMap]
<< "http://pastebin.com/raw/pFsb4ZBS";

Which defines all the color maps as downvalues of MPLColorMap. You can now access the color maps like

MPLColorMap["Magma"][.8]

Mathematica graphics

and use them via

DensityPlot[Sin[x - y], {x, -3, 3}, {y, -3, 3}, 
 ColorFunction -> MPLColorMap["Viridis"]]

Mathematica graphics

Here are all the new color maps shown using the showcolorfunction defined here,

showcolorfunction[MPLColorMap[#]] & /@ {"Magma", "Inferno", "Plasma", 
  "Viridis", "EricsRdBuGnYl", "EricsRdBuGnYl2", "EricsPuBuGnYl", 
  "FakeParula", "JoesBluGrnPnk2"}

This is great! Thanks for the efforts! I'm still going to accept @george2079 's answer, as it is a more compact form. Nevertheless I appreciate your work very much :) — DPF, Commented Sep 27, 2016 at 14:36
Your last edit makes the use of your variant very easy. Clear Like! — DPF, Commented Sep 27, 2016 at 14:52
Might be worth updating this, as the code as posted now throws errors because of changes in formatting I'm assuming. Might also be worth putting this kind of thing in the Data Repository? — b3m2a1, Commented Aug 20, 2020 at 5:30
@JasonB. I've made this into an official WFR item: resources.wolframcloud.com/FunctionRepository/resources/… ! Now it's very easy to use those colors. — swish, Commented Oct 22, 2021 at 17:59

J. M.'s missing motivation · Accepted Answer · 2018-10-10 02:26:52Z

Thanks to @yarchik, I made it work for Mathematica, by simply replacing [ and ] with { and } using a text editor:

viridis=Module[{colorlist},
colorlist={{0.26700401,0.00487433,0.32941519},{0.26851048,0.00960483,0.33542652},{0.26994384,0.01462494,0.34137895},{0.27130489,0.01994186,0.34726862},{0.27259384,0.02556309,0.35309303},{0.27380934,0.03149748,0.35885256},{0.27495242,0.03775181,0.36454323},{0.27602238,0.04416723,0.37016418},{0.2770184,0.05034437,0.37571452},{0.27794143,0.05632444,0.38119074},{0.27879067,0.06214536,0.38659204},{0.2795655,0.06783587,0.39191723},{0.28026658,0.07341724,0.39716349},{0.28089358,0.07890703,0.40232944},{0.28144581,0.0843197,0.40741404},{0.28192358,0.08966622,0.41241521},{0.28232739,0.09495545,0.41733086},{0.28265633,0.10019576,0.42216032},{0.28291049,0.10539345,0.42690202},{0.28309095,0.11055307,0.43155375},{0.28319704,0.11567966,0.43611482},{0.28322882,0.12077701,0.44058404},{0.28318684,0.12584799,0.44496},{0.283072,0.13089477,0.44924127},{0.28288389,0.13592005,0.45342734},{0.28262297,0.14092556,0.45751726},{0.28229037,0.14591233,0.46150995},{0.28188676,0.15088147,0.46540474},{0.28141228,0.15583425,0.46920128},{0.28086773,0.16077132,0.47289909},{0.28025468,0.16569272,0.47649762},{0.27957399,0.17059884,0.47999675},{0.27882618,0.1754902,0.48339654},{0.27801236,0.18036684,0.48669702},{0.27713437,0.18522836,0.48989831},{0.27619376,0.19007447,0.49300074},{0.27519116,0.1949054,0.49600488},{0.27412802,0.19972086,0.49891131},{0.27300596,0.20452049,0.50172076},{0.27182812,0.20930306,0.50443413},{0.27059473,0.21406899,0.50705243},{0.26930756,0.21881782,0.50957678},{0.26796846,0.22354911,0.5120084},{0.26657984,0.2282621,0.5143487},{0.2651445,0.23295593,0.5165993},{0.2636632,0.23763078,0.51876163},{0.26213801,0.24228619,0.52083736},{0.26057103,0.2469217,0.52282822},{0.25896451,0.25153685,0.52473609},{0.25732244,0.2561304,0.52656332},{0.25564519,0.26070284,0.52831152},{0.25393498,0.26525384,0.52998273},{0.25219404,0.26978306,0.53157905},{0.25042462,0.27429024,0.53310261},{0.24862899,0.27877509,0.53455561},{0.2468114,0.28323662,0.53594093},{0.24497208,0.28767547,0.53726018},{0.24311324,0.29209154,0.53851561},{0.24123708,0.29648471,0.53970946},{0.23934575,0.30085494,0.54084398},{0.23744138,0.30520222,0.5419214},{0.23552606,0.30952657,0.54294396},{0.23360277,0.31382773,0.54391424},{0.2316735,0.3181058,0.54483444},{0.22973926,0.32236127,0.54570633},{0.22780192,0.32659432,0.546532},{0.2258633,0.33080515,0.54731353},{0.22392515,0.334994,0.54805291},{0.22198915,0.33916114,0.54875211},{0.22005691,0.34330688,0.54941304},{0.21812995,0.34743154,0.55003755},{0.21620971,0.35153548,0.55062743},{0.21429757,0.35561907,0.5511844},{0.21239477,0.35968273,0.55171011},{0.2105031,0.36372671,0.55220646},{0.20862342,0.36775151,0.55267486},{0.20675628,0.37175775,0.55311653},{0.20490257,0.37574589,0.55353282},{0.20306309,0.37971644,0.55392505},{0.20123854,0.38366989,0.55429441},{0.1994295,0.38760678,0.55464205},{0.1976365,0.39152762,0.55496905},{0.19585993,0.39543297,0.55527637},{0.19410009,0.39932336,0.55556494},{0.19235719,0.40319934,0.55583559},{0.19063135,0.40706148,0.55608907},{0.18892259,0.41091033,0.55632606},{0.18723083,0.41474645,0.55654717},{0.18555593,0.4185704,0.55675292},{0.18389763,0.42238275,0.55694377},{0.18225561,0.42618405,0.5571201},{0.18062949,0.42997486,0.55728221},{0.17901879,0.43375572,0.55743035},{0.17742298,0.4375272,0.55756466},{0.17584148,0.44128981,0.55768526},{0.17427363,0.4450441,0.55779216},{0.17271876,0.4487906,0.55788532},{0.17117615,0.4525298,0.55796464},{0.16964573,0.45626209,0.55803034},{0.16812641,0.45998802,0.55808199},{0.1666171,0.46370813,0.55811913},{0.16511703,0.4674229,0.55814141},{0.16362543,0.47113278,0.55814842},{0.16214155,0.47483821,0.55813967},{0.16066467,0.47853961,0.55811466},{0.15919413,0.4822374,0.5580728},{0.15772933,0.48593197,0.55801347},{0.15626973,0.4896237,0.557936},{0.15481488,0.49331293,0.55783967},{0.15336445,0.49700003,0.55772371},{0.1519182,0.50068529,0.55758733},{0.15047605,0.50436904,0.55742968},{0.14903918,0.50805136,0.5572505},{0.14760731,0.51173263,0.55704861},{0.14618026,0.51541316,0.55682271},{0.14475863,0.51909319,0.55657181},{0.14334327,0.52277292,0.55629491},{0.14193527,0.52645254,0.55599097},{0.14053599,0.53013219,0.55565893},{0.13914708,0.53381201,0.55529773},{0.13777048,0.53749213,0.55490625},{0.1364085,0.54117264,0.55448339},{0.13506561,0.54485335,0.55402906},{0.13374299,0.54853458,0.55354108},{0.13244401,0.55221637,0.55301828},{0.13117249,0.55589872,0.55245948},{0.1299327,0.55958162,0.55186354},{0.12872938,0.56326503,0.55122927},{0.12756771,0.56694891,0.55055551},{0.12645338,0.57063316,0.5498411},{0.12539383,0.57431754,0.54908564},{0.12439474,0.57800205,0.5482874},{0.12346281,0.58168661,0.54744498},{0.12260562,0.58537105,0.54655722},{0.12183122,0.58905521,0.54562298},{0.12114807,0.59273889,0.54464114},{0.12056501,0.59642187,0.54361058},{0.12009154,0.60010387,0.54253043},{0.11973756,0.60378459,0.54139999},{0.11951163,0.60746388,0.54021751},{0.11942341,0.61114146,0.53898192},{0.11948255,0.61481702,0.53769219},{0.11969858,0.61849025,0.53634733},{0.12008079,0.62216081,0.53494633},{0.12063824,0.62582833,0.53348834},{0.12137972,0.62949242,0.53197275},{0.12231244,0.63315277,0.53039808},{0.12344358,0.63680899,0.52876343},{0.12477953,0.64046069,0.52706792},{0.12632581,0.64410744,0.52531069},{0.12808703,0.64774881,0.52349092},{0.13006688,0.65138436,0.52160791},{0.13226797,0.65501363,0.51966086},{0.13469183,0.65863619,0.5176488},{0.13733921,0.66225157,0.51557101},{0.14020991,0.66585927,0.5134268},{0.14330291,0.66945881,0.51121549},{0.1466164,0.67304968,0.50893644},{0.15014782,0.67663139,0.5065889},{0.15389405,0.68020343,0.50417217},{0.15785146,0.68376525,0.50168574},{0.16201598,0.68731632,0.49912906},{0.1663832,0.69085611,0.49650163},{0.1709484,0.69438405,0.49380294},{0.17570671,0.6978996,0.49103252},{0.18065314,0.70140222,0.48818938},{0.18578266,0.70489133,0.48527326},{0.19109018,0.70836635,0.48228395},{0.19657063,0.71182668,0.47922108},{0.20221902,0.71527175,0.47608431},{0.20803045,0.71870095,0.4728733},{0.21400015,0.72211371,0.46958774},{0.22012381,0.72550945,0.46622638},{0.2263969,0.72888753,0.46278934},{0.23281498,0.73224735,0.45927675},{0.2393739,0.73558828,0.45568838},{0.24606968,0.73890972,0.45202405},{0.25289851,0.74221104,0.44828355},{0.25985676,0.74549162,0.44446673},{0.26694127,0.74875084,0.44057284},{0.27414922,0.75198807,0.4366009},{0.28147681,0.75520266,0.43255207},{0.28892102,0.75839399,0.42842626},{0.29647899,0.76156142,0.42422341},{0.30414796,0.76470433,0.41994346},{0.31192534,0.76782207,0.41558638},{0.3198086,0.77091403,0.41115215},{0.3277958,0.77397953,0.40664011},{0.33588539,0.7770179,0.40204917},{0.34407411,0.78002855,0.39738103},{0.35235985,0.78301086,0.39263579},{0.36074053,0.78596419,0.38781353},{0.3692142,0.78888793,0.38291438},{0.37777892,0.79178146,0.3779385},{0.38643282,0.79464415,0.37288606},{0.39517408,0.79747541,0.36775726},{0.40400101,0.80027461,0.36255223},{0.4129135,0.80304099,0.35726893},{0.42190813,0.80577412,0.35191009},{0.43098317,0.80847343,0.34647607},{0.44013691,0.81113836,0.3409673},{0.44936763,0.81376835,0.33538426},{0.45867362,0.81636288,0.32972749},{0.46805314,0.81892143,0.32399761},{0.47750446,0.82144351,0.31819529},{0.4870258,0.82392862,0.31232133},{0.49661536,0.82637633,0.30637661},{0.5062713,0.82878621,0.30036211},{0.51599182,0.83115784,0.29427888},{0.52577622,0.83349064,0.2881265},{0.5356211,0.83578452,0.28190832},{0.5455244,0.83803918,0.27562602},{0.55548397,0.84025437,0.26928147},{0.5654976,0.8424299,0.26287683},{0.57556297,0.84456561,0.25641457},{0.58567772,0.84666139,0.24989748},{0.59583934,0.84871722,0.24332878},{0.60604528,0.8507331,0.23671214},{0.61629283,0.85270912,0.23005179},{0.62657923,0.85464543,0.22335258},{0.63690157,0.85654226,0.21662012},{0.64725685,0.85839991,0.20986086},{0.65764197,0.86021878,0.20308229},{0.66805369,0.86199932,0.19629307},{0.67848868,0.86374211,0.18950326},{0.68894351,0.86544779,0.18272455},{0.69941463,0.86711711,0.17597055},{0.70989842,0.86875092,0.16925712},{0.72039115,0.87035015,0.16260273},{0.73088902,0.87191584,0.15602894},{0.74138803,0.87344918,0.14956101},{0.75188414,0.87495143,0.14322828},{0.76237342,0.87642392,0.13706449},{0.77285183,0.87786808,0.13110864},{0.78331535,0.87928545,0.12540538},{0.79375994,0.88067763,0.12000532},{0.80418159,0.88204632,0.11496505},{0.81457634,0.88339329,0.11034678},{0.82494028,0.88472036,0.10621724},{0.83526959,0.88602943,0.1026459},{0.84556056,0.88732243,0.09970219},{0.8558096,0.88860134,0.09745186},{0.86601325,0.88986815,0.09595277},{0.87616824,0.89112487,0.09525046},{0.88627146,0.89237353,0.09537439},{0.89632002,0.89361614,0.09633538},{0.90631121,0.89485467,0.09812496},{0.91624212,0.89609127,0.1007168},{0.92610579,0.89732977,0.10407067},{0.93590444,0.8985704,0.10813094},{0.94563626,0.899815,0.11283773},{0.95529972,0.90106534,0.11812832},{0.96489353,0.90232311,0.12394051},{0.97441665,0.90358991,0.13021494},{0.98386829,0.90486726,0.13689671},{0.99324789,0.90615657,0.1439362}};
Evaluate[Blend[RGBColor @@@ colorlist, #] &]
];
BarLegend[{viridis, {0, 1}}]

Edit:

Another Example to visualize the grayscale-improvement ("Rainbow" vs. viridis):

mPlots = ContourPlot[Cos[x] Sin[y], {x, -10, 10}, {y, -10, 10}, PlotRange -> All, ColorFunction -> #, PlotPoints -> 75, ImageSize -> Medium] & /@
    {"Rainbow", viridis}
mPlots /. x: _RGBColor | _Hue | _CMYKColor :> ColorConvert[x, "Grayscale"]

george2079 · Accepted Answer · 2016-09-27 14:59:29Z

we should not need to manually fix the format.. cut-paste from https://github.com/BIDS/colormap/blob/master/option_b.py

pyarray = " [[  1.46159096e-03,   4.66127766e-04,   1.38655200e-02],
   [  2.26726368e-03,   1.26992553e-03,   1.85703520e-02],
   [  3.29899092e-03,   2.24934863e-03,   2.42390508e-02],
   [  4.54690615e-03,   3.39180156e-03,   3.09092475e-02],
   [  6.00552565e-03,   4.69194561e-03,   3.85578980e-02],
   [  7.67578856e-03,   6.13611626e-03,   4.68360336e-02],
   [  9.56051094e-03,   7.71344131e-03,   5.51430756e-02],
   [  1.16634769e-02,   9.41675403e-03,   6.34598080e-02],
   [  1.39950388e-02,   1.12247138e-02,   7.18616890e-02],
   [  1.65605595e-02,   1.31362262e-02,   8.02817951e-02],
   [  1.93732295e-02,   1.51325789e-02,   8.87668094e-02],
   [  2.24468865e-02,   1.71991484e-02,   9.73274383e-02],
   [  2.57927373e-02,   1.93306298e-02,   1.05929835e-01],
   [  2.94324251e-02,   2.15030771e-02,   1.14621328e-01],
   [  3.33852235e-02,   2.37024271e-02,   1.23397286e-01],
   [  3.76684211e-02,   2.59207864e-02,   1.32232108e-01],
   [  4.22525554e-02,   2.81385015e-02,   1.41140519e-01],
   [  4.69146287e-02,   3.03236129e-02,   1.50163867e-01],
   [  5.16437624e-02,   3.24736172e-02,   1.59254277e-01],
   [  5.64491009e-02,   3.45691867e-02,   1.68413539e-01],
   [  6.13397200e-02,   3.65900213e-02,   1.77642172e-01],
   [  6.63312620e-02,   3.85036268e-02,   1.86961588e-01],
   [  7.14289181e-02,   4.02939095e-02,   1.96353558e-01],
   [  7.66367560e-02,   4.19053329e-02,   2.05798788e-01],
   [  8.19620773e-02,   4.33278666e-02,   2.15289113e-01],
   [  8.74113897e-02,   4.45561662e-02,   2.24813479e-01],
   [  9.29901526e-02,   4.55829503e-02,   2.34357604e-01],
   [  9.87024972e-02,   4.64018731e-02,   2.43903700e-01],
   [  1.04550936e-01,   4.70080541e-02,   2.53430300e-01],
   [  1.10536084e-01,   4.73986708e-02,   2.62912235e-01],
   [  1.16656423e-01,   4.75735920e-02,   2.72320803e-01],
   [  1.22908126e-01,   4.75360183e-02,   2.81624170e-01],
   [  1.29284984e-01,   4.72930838e-02,   2.90788012e-01],
   [  1.35778450e-01,   4.68563678e-02,   2.99776404e-01],
   [  1.42377819e-01,   4.62422566e-02,   3.08552910e-01],
   [  1.49072957e-01,   4.54676444e-02,   3.17085139e-01],
   [  1.55849711e-01,   4.45588056e-02,   3.25338414e-01],
   [  1.62688939e-01,   4.35542881e-02,   3.33276678e-01],
   [  1.69575148e-01,   4.24893149e-02,   3.40874188e-01],
   [  1.76493202e-01,   4.14017089e-02,   3.48110606e-01],
   [  1.83428775e-01,   4.03288858e-02,   3.54971391e-01],
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   [  9.46391536e-01,   9.30760752e-01,   4.42367495e-01],
   [  9.46402951e-01,   9.37158971e-01,   4.58591507e-01],
   [  9.46902568e-01,   9.43347775e-01,   4.74969778e-01],
   [  9.47936825e-01,   9.49317522e-01,   4.91426053e-01],
   [  9.49544830e-01,   9.55062900e-01,   5.07859649e-01],
   [  9.51740304e-01,   9.60586693e-01,   5.24203026e-01],
   [  9.54529281e-01,   9.65895868e-01,   5.40360752e-01],
   [  9.57896053e-01,   9.71003330e-01,   5.56275090e-01],
   [  9.61812020e-01,   9.75924241e-01,   5.71925382e-01],
   [  9.66248822e-01,   9.80678193e-01,   5.87205773e-01],
   [  9.71161622e-01,   9.85282161e-01,   6.02154330e-01],
   [  9.76510983e-01,   9.89753437e-01,   6.16760413e-01],
   [  9.82257307e-01,   9.94108844e-01,   6.31017009e-01], [ 9.88362068e-01, 9.98364143e-01, 6.44924005e-01]]"

the tough part is converting the e- format:

pyArrayToList[p_String] := 
 ToExpression@
  StringReplace[
   p, {m : NumberString ~~ "e" ~~ exp : NumberString :> 
     m <> " 10^" <> exp, "[" -> "{", "]" -> "}"}]

inferno = With[{x = RGBColor @@@ pyArrayToList@pyarray}, Blend[x, #] &];
BarLegend[{inferno, {0, 1}}]

note per comment by @Kuba this works as well:

inferno = With[{x=RGBColor @@@ ImportString[pyarray, "JSON"]},Blend[x, #] &];

the StringReplace is actually a tad faster, but not so much to make a difference.

$\begingroup$ ImportString[ pyarray, "JSON" ] this should do too. $\endgroup$
– Kuba
Commented Sep 27, 2016 at 14:07 — Kuba, Commented Sep 27, 2016 at 14:07
$\begingroup$ @Kuba, yes it does..thanks $\endgroup$
– george2079
Commented Sep 27, 2016 at 14:12 — george2079, Commented Sep 27, 2016 at 14:12

J. M.'s missing motivation · Accepted Answer · 2019-08-12 09:42:25Z

Many months ago, I decided to make "reduced" versions of the popular color gradients from Matplotlib, as well as the parula colormap from MATLAB. (I previously blogged about parula here.)

These are "reduced" in the sense that unlike the original colormaps that need to keep an array of 256 RGB triplets around, I was able to pare down the list of colors to a smaller portion, while still preserving the features of the color gradient. Since Blend[] is fine with handling non-equispaced colors, one can use it with these "reduced" color gradients.

I posted these colormaps here and here. (Update: "cividis", a color-blind-friendly variation of "viridis" presented in this paper, is now also implemented.)

To load these gradients into Mathematica, evaluate e.g.

Get["https://pastebin.com/raw/qcyE3vzF"]

To use the color gradients, just evaluate makeBlend[colorName]; e.g.

ContourPlot[Sin[x + Cos[y]] Cos[Sin[x] + y], {x, -3 π, 3 π}, {y, -3 π, 3 π}, 
            ColorFunction -> makeBlend["Parula"], PlotPoints -> 75]

contour plot colored with parula

Here is how the color gradients look, as well as the result of converting them to grayscale with ColorConvert[], and applying color blindness effects to them with ImageEffect[]:

reduced gradients

I will continue this discussion with a specific example, the "viridis" color gradient. We can use Kovesi's test image to see how "viridis" performs after being transformed. First, generate the test image:

kovesi = Block[{nc = 64 + 1/2, pixc = 8, a = 1/20, w, h},
               w = pixc nc + 1; h = Round[(w - 1)/4];
               Image[N[Join[Outer[Times, (Range[h, 1, -1]/(h - 1))^2,
                                  -a Cos[2 π Range[0, w - 1]/pixc]] + 
                            ConstantArray[Subdivide[a, 1 - a, w - 1], h], 
                            ConstantArray[Subdivide[w - 1], Round[h/4]]]]]]

Kovesi's test image

We can use Colorize[] to test "viridis":

img = Colorize[kovesi, ColorFunction -> makeBlend["Viridis"]]

Kovesi image, viridis colormap

Convert to grayscale:

ColorConvert[img, GrayLevel]

Kovesi image, grayscale conversion

How a protanopic person might see the image:

ImageEffect[img, {"ColorBlindness", "Protanopia"}]

Kovesi image, protanopic coloration

b3m2a1 · Accepted Answer · 2020-08-20 06:37:37Z

Basically an update on what Jason B. has already but with the addition of some stuff for making pretty Format forms / faking a proper ColorDataFunction:


getPyArray[url_] :=
 ToExpression@StringReplace[
   "[" <>
    Riffle[
     StringCases[
      Import[URL[url], "Text"],
      Whitespace ~~ "[" ~~
       Whitespace ~~ 
       NumberString ~~ (("e" ~~ NumberString) | "") ~~ "," ~~
       
       Whitespace ~~ NumberString ~~ (("e" ~~ NumberString) | "") ~~ "," ~~
  
            Whitespace ~~ NumberString ~~ (("e" ~~ NumberString) | "") ~~ "]"
      ],
     ","
     ] <> "]",
   {
    "e" -> "*^",
    "[" -> "{",
    "]" -> "}"
    }]

Unprotect[ColorDataFunction];
(* hacked this from the ColorDataFunction FormatValues and Subvalues *)

MakeBoxes[
   colf : ColorDataFunction[ scheme_, "Matplotlib",  range_, cf_Function],  
   fmt_
   ] :=
  With[{ thumbBoxes = LinearGradientImage[cf, {100, 15}], 
    rangeBoxes = MakeBoxes[ range, fmt]},
   BoxForm`ArrangeSummaryBox[
    ColorDataFunction,
    colf,
    None,
    {
     BoxForm`MakeSummaryItem[{"Name:", scheme}, fmt],
      BoxForm`MakeSummaryItem[{"Gradient:", thumbBoxes}, fmt]
     },
    {
      BoxForm`MakeSummaryItem[{"Domain:", range}, fmt],
     BoxForm`MakeSummaryItem[{"Class:", "Matplotlib"}, fmt]
     },
    fmt
    ]
   ];
ColorDataFunction[ scheme_, "Matplotlib", range_, f_][ x_] := Quiet[ f[ x]]
Protect[ColorDataFunction];
$MPLColorMaps =
  MapThread[
    # ->
      With[{d = RGBColor @@@ getPyArray[#2]},
       ColorDataFunction[#, "Matplotlib", {0, 1}, Blend[d, #] &]
       ] &,
    {
     {"Magma", "Inferno", "Plasma", "Viridis", "EricsRdBuGnYl", 
      "EricsRdBuGnYl2", "EricsPuBuGnYl", "FakeParula", "JoesBluGrnPnk2"},
     {"https://raw.githubusercontent.com/BIDS/colormap/master/option_a.py", 
      "https://raw.githubusercontent.com/BIDS/colormap/master/option_b.py", 
      "https://raw.githubusercontent.com/BIDS/colormap/master/option_c.py", 
      "https://raw.githubusercontent.com/BIDS/colormap/master/option_d.py", 
      "https://github.com/BIDS/colormap/raw/master/erics-RdBuGnYl_r.py", 
      "https://github.com/BIDS/colormap/raw/master/erics-RdBuGnYl_r_v2.py", 
      "https://github.com/BIDS/colormap/raw/master/erics_PuBuGnYl_r.py", 
      "https://github.com/BIDS/colormap/raw/master/fake_parula.py", 
      "https://github.com/BIDS/colormap/raw/master/joes-blu_grn_pnk2.py"}
     }
    ] // Association;

Here's what they look like

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