RGB to HSL

rgb-to-hsl.ts

/**
 * @see https://de.wikipedia.org/wiki/HSV-Farbraum#Umrechnung_RGB_in_HSV/HSL
 */
private convertRgbToHsl(rgbColor: { r: number; g: number; b: number; }): { h: number; s: number; l: number; } {
  let h: number;
  let s: number;
  let l: number;

  let { r, g, b } = rgbColor;
  [ r, g, b ] = [ r, g, b ].map((value) => value / 255);

  const max = Math.max(r, g, b);
  const min = Math.min(r, g, b);

  if (max === min) {
    h = 0;
  } else if (max === r) {
    h = 60 * ((g - b) / (max - min));
  } else if (max === g) {
    h = 60 * (2 + (b - r) / (max - min));
  } else if (max === b) {
    h = 60 * (4 + (r - g) / (max - min));
  }

  if (h < 0) {
    h += 360;
  }

  if (max === 0 || min === 1) {
    s = 0;
  } else {
    s = ((max - min) / (1 - Math.abs(max + min - 1))) * 100;
  }

  l = (max + min) / 2 * 100;

  [ h, s, l ] = [ h, s, l ].map((value) => Math.round(value));

  return { h, s, l };
}