Color conversion and tool with RGB & hexadecimal code.

format.color.ts

// Working in all environments
// https://stackoverflow.com/a/39077686

/**
 * Converting RGB to hex
 * @param r red
 * @param g green
 * @param b blue
 * @returns Hexacode color
 * @example rgbToHex(0, 51, 255); // '#0033ff'
 */
export const rgbToHex = (r: number, g: number, b: number): string => {
  return (
    '#' +
    [r, g, b]
      .map((x) => {
        const hex = x.toString(16);
        return hex.length === 1 ? '0' + hex : hex;
      })
      .join('')
  );
};

/**
 * Converting hex to RGB
 * Works also with shorthand hex triplets such as "#03F".
 * @param hex Hexacode color
 * @returns RGB color object {r, g, b}
 * @example hexToRgb("#0033ff"); // {r:0, g:51, b:255}
 * @example hexToRgb("#03f"); // {r:0, g:51, b:255}
 */
export const hexToRgb = (hex: string): { r: number; g: number; b: number } | null => {
  const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
  return result
    ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16),
      }
    : null;
};

//(2017) SIMPLE ES6 composable arrow functions
// https://stackoverflow.com/a/42429333

export const arrayToRGBString = (rgb: number[]): string => `rgb(${rgb.join(',')})`;
export const hexToRGBArray = (hex: string): number[] | undefined =>
  hex?.match(/[A-Za-z0-9]{2}/g)?.map((v) => parseInt(v, 16));
export const rgbArrayToHex = (rgb: number[]): string => `#${rgb.map((v) => v.toString(16).padStart(2, '0')).join('')}`;
export const rgbStringToArray = (rgb: string): number[] | undefined =>
  rgb
    ?.match(/^rgb\((\d+),\s*(\d+),\s*(\d+)\)$/)
    ?.splice(1, 3)
    ?.map((v) => Number(v));
export const rgbStringToHex = (rgb: string): string | undefined =>
  rgb != undefined
    ? rgbStringToArray(rgb) != undefined
      ? rgbArrayToHex(rgbStringToArray(rgb) as number[])
      : undefined
    : undefined;


// https://stackoverflow.com/a/21924155

export const hexToComplementary = (hex: number): string => ('000000' + (0xffffff ^ hex).toString(16)).slice(-6);