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Update contrast function and tests, fixes #2743 #2754

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Mar 15, 2016
Merged

Update contrast function and tests, fixes #2743 #2754

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40 changes: 24 additions & 16 deletions lib/less/functions/color.js
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Original file line number Diff line number Diff line change
Expand Up @@ -263,33 +263,41 @@ colorFunctions = {
greyscale: function (color) {
return colorFunctions.desaturate(color, new Dimension(100));
},
contrast: function (color, dark, light, threshold) {
contrast: function (color, color1, color2, threshold) {
// Return which of `color1` and `color2` has the greatest contrast with `color`
// according to the standard WCAG contrast ratio calculation.
// https://www.w3.org/TR/WCAG20/#contrast-ratiodef
// The threshold param is no longer used, in line with SASS.
// filter: contrast(3.2);
// should be kept as is, so check for color
if (!color.rgb) {
return null;
}
if (typeof light === 'undefined') {
light = colorFunctions.rgba(255, 255, 255, 1.0);
if (typeof color1 === 'undefined') {
color1 = colorFunctions.rgba(0, 0, 0, 1.0);
}
if (typeof dark === 'undefined') {
dark = colorFunctions.rgba(0, 0, 0, 1.0);
if (typeof color2 === 'undefined') {
color2 = colorFunctions.rgba(255, 255, 255, 1.0);
}
//Figure out which is actually light and dark!
if (dark.luma() > light.luma()) {
var t = light;
light = dark;
dark = t;
var contrast1, contrast2;
var luma = color.luma();
var luma1 = color1.luma();
var luma2 = color2.luma();
// Calculate contrast ratios for each color
if (luma > luma1) {
contrast1 = (luma + 0.05) / (luma1 + 0.05);
} else {
contrast1 = (luma1 + 0.05) / (luma + 0.05);
}
if (typeof threshold === 'undefined') {
threshold = 0.43;
if (luma > luma2) {
contrast2 = (luma + 0.05) / (luma2 + 0.05);
} else {
threshold = number(threshold);
contrast2 = (luma2 + 0.05) / (luma + 0.05);
}
if (color.luma() < threshold) {
return light;
if (contrast1 > contrast2) {
return color1;
} else {
return dark;
return color2;
}
},
argb: function (color) {
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6 changes: 3 additions & 3 deletions test/css/functions.css
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,7 @@
saturate-filter: saturate(5%);
contrast-white: #000000;
contrast-black: #ffffff;
contrast-red: #ffffff;
contrast-red: #000000;
contrast-green: #000000;
contrast-blue: #ffffff;
contrast-yellow: #000000;
Expand All @@ -49,11 +49,11 @@
contrast-light-thresh: #111111;
contrast-dark-thresh: #eeeeee;
contrast-high-thresh: #eeeeee;
contrast-low-thresh: #111111;
contrast-low-thresh: #eeeeee;
contrast-light-thresh-per: #111111;
contrast-dark-thresh-per: #eeeeee;
contrast-high-thresh-per: #eeeeee;
contrast-low-thresh-per: #111111;
contrast-low-thresh-per: #eeeeee;
replace: "Hello, World!";
replace-captured: "This is a new string.";
replace-with-flags: "2 + 2 = 4";
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