src/theme/color-contrast.scss
/**
* Hightly based on: "Using Sass to automatically pick text colors"
* https://medium.com/dev-channel/using-sass-to-automatically-pick-text-colors-4ba7645d2796
*/
/**
* Precomputed linear color channel values, for use in contrast calculations.
* See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests
* ---
*
* Algorithm, for c in 0 to 255:
* f(c) {
* c = c / 255;
* return c < 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
* }
*
* This lookup table is needed since there is no `pow` in SASS.
*
* ---
* @access private
* @type Map
* @group themes
*/
$md-linear-channel-values:
0
.0003035269835488375
.000607053967097675
.0009105809506465125
.00121410793419535
.0015176349177441874
.001821161901293025
.0021246888848418626
.0024282158683907
.0027317428519395373
.003035269835488375
.003346535763899161
.003676507324047436
.004024717018496307
.004391442037410293
.004776953480693729
.005181516702338386
.005605391624202723
.006048833022857054
.006512090792594475
.006995410187265387
.007499032043226175
.008023192985384994
.008568125618069307
.009134058702220787
.00972121732023785
.010329823029626936
.010960094006488246
.011612245179743885
.012286488356915872
.012983032342173012
.013702083047289686
.014443843596092545
.01520851442291271
.01599629336550963
.016807375752887384
.017641954488384078
.018500220128379697
.019382360956935723
.0202885630566524
.021219010376003555
.022173884793387385
.02315336617811041
.024157632448504756
.02518685962736163
.026241221894849898
.027320891639074894
.028426039504420793
.0295568344378088
.030713443732993635
.03189603307301153
.033104766570885055
.03433980680868217
.03560131487502034
.03688945040110004
.0382043715953465
.03954623527673284
.04091519690685319
.042311410620809675
.043735029256973465
.04518620438567554
.046665086336880095
.04817182422688942
.04970656598412723
.05126945837404324
.052860647023180246
.05448027644244237
.05612849004960009
.05780543019106723
.0595112381629812
.06124605423161761
.06301001765316767
.06480326669290577
.06662593864377289
.06847816984440017
.07036009569659588
.07227185068231748
.07421356838014963
.07618538148130785
.07818742180518633
.08021982031446832
.0822827071298148
.08437621154414882
.08650046203654976
.08865558628577294
.09084171118340768
.09305896284668745
.0953074666309647
.09758734714186246
.09989872824711389
.10224173308810132
.10461648409110419
.10702310297826761
.10946171077829933
.1119324278369056
.11443537382697373
.11697066775851084
.11953842798834562
.12213877222960187
.12477181756095049
.12743768043564743
.1301364766903643
.13286832155381798
.13563332965520566
.13843161503245183
.14126329114027164
.14412847085805777
.14702726649759498
.14995978981060856
.15292615199615017
.1559264637078274
.1589608350608804
.162029375639111
.1651321945016676
.16826940018969075
.1714411007328226
.17464740365558504
.17788841598362912
.18116424424986022
.184474994500441
.18782077230067787
.19120168274079138
.1946178304415758
.19806931955994886
.20155625379439707
.20507873639031693
.20863687014525575
.21223075741405523
.21586050011389926
.2195261997292692
.2232279573168085
.22696587351009836
.23074004852434915
.23455058216100522
.238397573812271
.24228112246555486
.24620132670783548
.25015828472995344
.25415209433082675
.2581828529215958
.26225065752969623
.26635560480286247
.2704977910130658
.27467731206038465
.2788942634768104
.2831487404299921
.2874408377269175
.29177064981753587
.2961382707983211
.3005437944157765
.3049873140698863
.30946892281750854
.31398871337571754
.31854677812509186
.32314320911295075
.3277780980565422
.33245153634617935
.33716361504833037
.3419144249086609
.3467040563550296
.35153259950043936
.3564001441459435
.3613067797835095
.3662525955988395
.3712376804741491
.3762621229909065
.38132601143253014
.386429433787049
.39157247774972326
.39675523072562685
.4019777798321958
.4072402119017367
.41254261348390375
.4178850708481375
.4232676699860717
.4286904966139066
.43415363617474895
.4396571738409188
.44520119451622786
.45078578283822346
.45641102318040466
.4620769996544071
.467783796112159
.47353149614800955
.4793201831008268
.4851499400560704
.4910208498478356
.4969329950608704
.5028864580325687
.5088813208549338
.5149176653765214
.5209955732043543
.5271151257058131
.5332764040105052
.5394794890121072
.5457244613701866
.5520114015120001
.5583403896342679
.5647115057049292
.5711248294648731
.5775804404296506
.5840784178911641
.5906188409193369
.5972017883637634
.6038273388553378
.6104955708078648
.6172065624196511
.6239603916750761
.6307571363461468
.6375968739940326
.6444796819705821
.6514056374198242
.6583748172794485
.665387298282272
.6724431569576875
.6795424696330938
.6866853124353135
.6938717612919899
.7011018919329731
.7083757798916868
.7156935005064807
.7230551289219693
.7304607400903537
.7379104087727308
.7454042095403874
.7529422167760779
.7605245046752924
.768151147247507
.7758222183174236
.7835377915261935
.7912979403326302
.799102738014409
.8069522576692516
.8148465722161012
.8227857543962835
.8307698767746546
.83879901174074
.846873231509858
.8549926081242338
.8631572134541023
.8713671191987972
.8796223968878317
.8879231178819663
.8962693533742664
.9046611743911496
.9130986517934192
.9215818562772946
.9301108583754237
.938685728457888
.9473065367331999
.9559733532492861
.9646862478944651
.9734452903984125
.9822505503331171
.9911020971138298
1;
/**
* Calculate the luminance for a color.
* ---
* @access private
* ---
* @param {string} $color — The color to be analysed
*/
@function md-check-luminance($color) {
$red: nth($md-linear-channel-values, red($color) + 1);
$green: nth($md-linear-channel-values, green($color) + 1);
$blue: nth($md-linear-channel-values, blue($color) + 1);
@return .2126 * $red + .7152 * $green + .0722 * $blue;
}
/**
* Calculate the contrast ratio between two colors.
* ---
* @access private
* ---
* @param {string} $bg — The bg color
* @param {string} $fg — The fg color to be compared
*/
@function md-calculate-contrast($bg, $fg) {
$bgLum: md-check-luminance($bg) + .2;
$fgLum: md-check-luminance($fg) + .2;
@return max($bgLum, $fgLum) / min($bgLum, $fgLum);
}
/**
* Determine whether to use dark or light text on top of given color.
* Returns dark or light depending on the contrast ratio.
* ---
* @access private
* ---
* @param {string} $color — The desired color to be compared
*/
@function md-pick-contrast($color) {
$lightColor: map-get(map-get($md-color-levels, dark), text-primary);
$lightContrast: md-calculate-contrast($color, $lightColor);
$darkColor: map-get(map-get($md-color-levels, light), text-primary);
$darkContrast: md-calculate-contrast($color, $darkColor);
@if ($lightContrast > $darkContrast) {
@return "dark";
}
@return "light";
}