https://css-tricks.com/converting-color-spaces-in-...
function RGBToHSL(r,g,b) {
// Make r, g, and b fractions of 1
r /= 255;
g /= 255;
b /= 255;
// Find greatest and smallest channel values
let cmin = Math.min(r,g,b),
cmax = Math.max(r,g,b),
delta = cmax - cmin,
h = 0,
s = 0,
l = 0;
// Calculate hue
// No difference
if (delta == 0)
h = 0;
// Red is max
else if (cmax == r)
h = ((g - b) / delta) % 6;
// Green is max
else if (cmax == g)
h = (b - r) / delta + 2;
// Blue is max
else
h = (r - g) / delta + 4;
h = Math.round(h * 60);
// Make negative hues positive behind 360°
if (h < 0)
h += 360;
// Calculate lightness
l = (cmax + cmin) / 2;
// Calculate saturation
s = delta == 0 ? 0 : delta / (1 - Math.abs(2 * l - 1));
// Multiply l and s by 100
s = +(s * 100).toFixed(1);
l = +(l * 100).toFixed(1);
return "hsl(" + h + "," + s + "%," + l + "%)";
}