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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | /**
* For a provided hex color, returns an inverted color for legibility.
* @param {[type]} hex - hexadecimal (HTML) color, e.g. #FFFFFF
* @param {[type]} bw - whether to return only black or white as inverted color
* @return {[type]} [description]
*/
export function invertColor(hex, bw = true) {
if (hex.indexOf('#') === 0) {
hex = hex.slice(1)
}
// convert 3-digit hex to 6-digits.
if (hex.length === 3) {
hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2]
}
if (hex.length !== 6) {
console.warn('Invalid HEX color.', hex)
}
let r = parseInt(hex.slice(0, 2), 16)
let g = parseInt(hex.slice(2, 4), 16)
let b = parseInt(hex.slice(4, 6), 16)
if (bw) {
// http://stackoverflow.com/a/3943023/112731
return r * 0.299 + g * 0.587 + b * 0.114 > 186 ? '#000000' : '#FFFFFF'
}
// invert color components
r = (255 - r).toString(16)
g = (255 - g).toString(16)
b = (255 - b).toString(16)
// pad each with zeros and return
return '#' + padZero(r) + padZero(g) + padZero(b)
}
export function padZero(str, len) {
len = len || 2
const zeros = new Array(len).join('0')
return (zeros + str).slice(-len)
}
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