utils.js

export function hslToHex(h, s, l) {
  l /= 100
  const a = s * Math.min(l, 1 - l) / 100
  const f = n => {
    const k = (n + h / 30) % 12
    const color = l - a * Math.max(Math.min(k - 3, 9 - k, 1), -1)
    // convert to Hex and prefix "0" if needed
    return Math.round(255 * color).toString(16).padStart(2, '0')
  }
  return `#${f(0)}${f(8)}${f(4)}`
}

export function rgbToHsl(r, g, b){
    r /= 255, g /= 255, b /= 255
    var max = Math.max(r, g, b), min = Math.min(r, g, b)
    var h, s, l = (max + min) / 2

    if(max === min){
        h = s = 0 // achromatic
    } else {
        var d = max - min
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min)
        switch(max) {
            case r: h = (g - b) / d + (g < b ? 6 : 0)
              break
            case g: h = (b - r) / d + 2
              break
            case b: h = (r - g) / d + 4
              break
        }
        h /= 6
    }

    h *= 100
    s *= 100
    l *= 100
    return [h, s, l]
}

export function rgbToHex(r, g, b) {
  return "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1)
}