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fix(color-contrast): correctly compute background color for elements with opacity #3944

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merged 16 commits into from
Mar 22, 2023
Merged

fix(color-contrast): correctly compute background color for elements with opacity #3944

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81e2a01
fix(create-grid): correctly compute stack order for non-positioned st…
straker Mar 3, 2023
46d3832
chore: Refactor createStackingOrder (#3932)
WilcoFiers Mar 6, 2023
e269217
use treewalker nodeIndex
straker Mar 8, 2023
b8bfb29
no floatpoint precision errors
straker Mar 8, 2023
f40d21a
pass nodeIndex to createGrid for shadowDom
straker Mar 8, 2023
b160c3d
do it properly
straker Mar 8, 2023
0cd2b0d
remove whitespace
straker Mar 8, 2023
08c7b09
fix(color-contrast): correctly handle opacity on parent elements
straker Mar 10, 2023
2137075
working
straker Mar 13, 2023
4678676
idea finalized
straker Mar 14, 2023
ea6bb04
remove comments
straker Mar 14, 2023
186723c
move function
straker Mar 14, 2023
e71dbb0
Merge branch 'develop' into color-contrast-opacity
straker Mar 15, 2023
2e43a29
tests!
straker Mar 15, 2023
5ad2ea3
fix comments
straker Mar 15, 2023
d29a302
fix stuff
straker Mar 20, 2023
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180 changes: 90 additions & 90 deletions lib/commons/color/color.js
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Original file line number Diff line number Diff line change
@@ -1,68 +1,7 @@
import standards from '../../standards';

/**
* Convert a CSS color value into a number
*/
function convertColorVal(colorFunc, value, index) {
if (/%$/.test(value)) {
//<percentage>
if (index === 3) {
// alpha
return parseFloat(value) / 100;
}
return (parseFloat(value) * 255) / 100;
}
if (colorFunc[index] === 'h') {
// hue
if (/turn$/.test(value)) {
return parseFloat(value) * 360;
}
if (/rad$/.test(value)) {
return parseFloat(value) * 57.3;
}
}
return parseFloat(value);
}

/**
* Convert HSL to RGB
*/
function hslToRgb([hue, saturation, lightness, alpha]) {
// Must be fractions of 1
saturation /= 255;
lightness /= 255;

const high = (1 - Math.abs(2 * lightness - 1)) * saturation;
const low = high * (1 - Math.abs(((hue / 60) % 2) - 1));
const base = lightness - high / 2;

let colors;
if (hue < 60) {
// red - yellow
colors = [high, low, 0];
} else if (hue < 120) {
// yellow - green
colors = [low, high, 0];
} else if (hue < 180) {
// green - cyan
colors = [0, high, low];
} else if (hue < 240) {
// cyan - blue
colors = [0, low, high];
} else if (hue < 300) {
// blue - purple
colors = [low, 0, high];
} else {
// purple - red
colors = [high, 0, low];
}

return colors
.map(color => {
return Math.round((color + base) * 255);
})
.concat(alpha);
}
const hexRegex = /^#[0-9a-f]{3,8}$/i;
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I took this opportunity to do something I've been wanting to do for awhile now which is convert the Color constructor function into a true class. The advantage to this was that I was able to do deepEquals on two Color objects whereas before that was not possible (thus greatly simplifying the tests). Another advantage is that all Color objects now share memory for all their functions thanks to the prototype whereas before each Color object had their own memory instance for each function.

const colorFnRegex = /^((?:rgb|hsl)a?)\s*\(([^\)]*)\)/i;

/**
* @class Color
Expand All @@ -72,18 +11,20 @@ function hslToRgb([hue, saturation, lightness, alpha]) {
* @param {number} blue
* @param {number} alpha
*/
function Color(red, green, blue, alpha = 1) {
/** @type {number} */
this.red = red;
export default class Color {
constructor(red, green, blue, alpha = 1) {
/** @type {number} */
this.red = red;

/** @type {number} */
this.green = green;
/** @type {number} */
this.green = green;

/** @type {number} */
this.blue = blue;
/** @type {number} */
this.blue = blue;

/** @type {number} */
this.alpha = alpha;
/** @type {number} */
this.alpha = alpha;
}

/**
* Provide the hex string value for the color
Expand All @@ -92,7 +33,7 @@ function Color(red, green, blue, alpha = 1) {
* @instance
* @return {string}
*/
this.toHexString = function toHexString() {
toHexString() {
var redString = Math.round(this.red).toString(16);
var greenString = Math.round(this.green).toString(16);
var blueString = Math.round(this.blue).toString(16);
Expand All @@ -102,23 +43,20 @@ function Color(red, green, blue, alpha = 1) {
(this.green > 15.5 ? greenString : '0' + greenString) +
(this.blue > 15.5 ? blueString : '0' + blueString)
);
};
}

this.toJSON = function toJSON() {
toJSON() {
const { red, green, blue, alpha } = this;
return { red, green, blue, alpha };
};

const hexRegex = /^#[0-9a-f]{3,8}$/i;
const colorFnRegex = /^((?:rgb|hsl)a?)\s*\(([^\)]*)\)/i;
}

/**
* Parse any valid color string and assign its values to "this"
* @method parseString
* @memberof axe.commons.color.Color
* @instance
*/
this.parseString = function parseString(colorString) {
parseString(colorString) {
// IE occasionally returns named colors instead of RGB(A) values
if (standards.cssColors[colorString] || colorString === 'transparent') {
const [red, green, blue] = standards.cssColors[colorString] || [0, 0, 0];
Expand All @@ -139,7 +77,7 @@ function Color(red, green, blue, alpha = 1) {
return this;
}
throw new Error(`Unable to parse color "${colorString}"`);
};
}

/**
* Set the color value based on a CSS RGB/RGBA string
Expand All @@ -149,7 +87,7 @@ function Color(red, green, blue, alpha = 1) {
* @instance
* @param {string} rgb The string value
*/
this.parseRgbString = function parseRgbString(colorString) {
parseRgbString(colorString) {
// IE can pass transparent as value instead of rgba
if (colorString === 'transparent') {
this.red = 0;
Expand All @@ -159,7 +97,7 @@ function Color(red, green, blue, alpha = 1) {
return;
}
this.parseColorFnString(colorString);
};
}

/**
* Set the color value based on a CSS RGB/RGBA string
Expand All @@ -169,7 +107,7 @@ function Color(red, green, blue, alpha = 1) {
* @instance
* @param {string} rgb The string value
*/
this.parseHexString = function parseHexString(colorString) {
parseHexString(colorString) {
if (!colorString.match(hexRegex) || [6, 8].includes(colorString.length)) {
return;
}
Expand All @@ -191,7 +129,7 @@ function Color(red, green, blue, alpha = 1) {
} else {
this.alpha = 1;
}
};
}

/**
* Set the color value based on a CSS RGB/RGBA string
Expand All @@ -201,7 +139,7 @@ function Color(red, green, blue, alpha = 1) {
* @instance
* @param {string} rgb The string value
*/
this.parseColorFnString = function parseColorFnString(colorString) {
parseColorFnString(colorString) {
const [, colorFunc, colorValStr] = colorString.match(colorFnRegex) || [];
if (!colorFunc || !colorValStr) {
return;
Expand All @@ -226,7 +164,7 @@ function Color(red, green, blue, alpha = 1) {
this.green = colorNums[1];
this.blue = colorNums[2];
this.alpha = typeof colorNums[3] === 'number' ? colorNums[3] : 1;
};
}

/**
* Get the relative luminance value
Expand All @@ -236,7 +174,7 @@ function Color(red, green, blue, alpha = 1) {
* @instance
* @return {number} The luminance value, ranges from 0 to 1
*/
this.getRelativeLuminance = function getRelativeLuminance() {
getRelativeLuminance() {
var rSRGB = this.red / 255;
var gSRGB = this.green / 255;
var bSRGB = this.blue / 255;
Expand All @@ -249,7 +187,69 @@ function Color(red, green, blue, alpha = 1) {
bSRGB <= 0.03928 ? bSRGB / 12.92 : Math.pow((bSRGB + 0.055) / 1.055, 2.4);

return 0.2126 * r + 0.7152 * g + 0.0722 * b;
};
}
}

/**
* Convert a CSS color value into a number
*/
function convertColorVal(colorFunc, value, index) {
if (/%$/.test(value)) {
//<percentage>
if (index === 3) {
// alpha
return parseFloat(value) / 100;
}
return (parseFloat(value) * 255) / 100;
}
if (colorFunc[index] === 'h') {
// hue
if (/turn$/.test(value)) {
return parseFloat(value) * 360;
}
if (/rad$/.test(value)) {
return parseFloat(value) * 57.3;
}
}
return parseFloat(value);
}

export default Color;
/**
* Convert HSL to RGB
*/
function hslToRgb([hue, saturation, lightness, alpha]) {
// Must be fractions of 1
saturation /= 255;
lightness /= 255;

const high = (1 - Math.abs(2 * lightness - 1)) * saturation;
const low = high * (1 - Math.abs(((hue / 60) % 2) - 1));
const base = lightness - high / 2;

let colors;
if (hue < 60) {
// red - yellow
colors = [high, low, 0];
} else if (hue < 120) {
// yellow - green
colors = [low, high, 0];
} else if (hue < 180) {
// green - cyan
colors = [0, high, low];
} else if (hue < 240) {
// cyan - blue
colors = [0, low, high];
} else if (hue < 300) {
// blue - purple
colors = [low, 0, high];
} else {
// purple - red
colors = [high, 0, low];
}

return colors
.map(color => {
return Math.round((color + base) * 255);
})
.concat(alpha);
}
36 changes: 20 additions & 16 deletions lib/commons/color/flatten-colors.js
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Original file line number Diff line number Diff line change
Expand Up @@ -88,37 +88,41 @@ function simpleAlphaCompositing(Cs, αs, Cb, αb, blendMode) {
* @method flattenColors
* @memberof axe.commons.color.Color
* @instance
* @param {Color} fgColor Foreground color
* @param {Color} bgColor Background color
* @param {Color} sourceColor Foreground color
* @param {Color} backdrop Background color
* @return {Color} Blended color
*/
function flattenColors(fgColor, bgColor, blendMode = 'normal') {
function flattenColors(sourceColor, backdrop, blendMode = 'normal') {
// foreground is the "source" color and background is the "backdrop" color
const r = simpleAlphaCompositing(
fgColor.red,
fgColor.alpha,
bgColor.red,
bgColor.alpha,
sourceColor.red,
sourceColor.alpha,
backdrop.red,
backdrop.alpha,
blendMode
);
const g = simpleAlphaCompositing(
fgColor.green,
fgColor.alpha,
bgColor.green,
bgColor.alpha,
sourceColor.green,
sourceColor.alpha,
backdrop.green,
backdrop.alpha,
blendMode
);
const b = simpleAlphaCompositing(
fgColor.blue,
fgColor.alpha,
bgColor.blue,
bgColor.alpha,
sourceColor.blue,
sourceColor.alpha,
backdrop.blue,
backdrop.alpha,
blendMode
);

// formula: αo = αs + αb x (1 - αs)
// clamp alpha between 0 and 1
const αo = clamp(fgColor.alpha + bgColor.alpha * (1 - fgColor.alpha), 0, 1);
const αo = clamp(
sourceColor.alpha + backdrop.alpha * (1 - sourceColor.alpha),
0,
1
);
if (αo === 0) {
return new Color(r, g, b, αo);
}
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