piling.js/src/utils/color-to-dec-alpha.js

A WebGL-based Library for Visual Piling/Stacking

const colorToDecAlpha = (color, defaultAlpha = 1) => {
  if (typeof color === 'string' || color instanceof String) {
    // HEX string, e.g., `#ff0000`
    if (color[0] === '#') return [parseInt(color.substr(1), 16), defaultAlpha];

    // RGBA string, e.g., `rgba(255, 0, 0, 0.5)`
    if (color.substring(0, 3) === 'rgb') {
      const matches = color.match(/(\d+),\s*(\d+),\s*(\d+),?\s*([\d.]+)?/);
      return [
        matches
          .slice(1, 4)
          // eslint-disable-next-line no-bitwise
          .map((x, i) => +x << (8 * (2 - i)))
          .reduce((x, sum) => sum + x, 0),
        Number.isNaN(+matches[4]) ? 1 : +matches[4],
      ];
    }

    // RGB string, e.g., `rgb(255, 0, 0)`
    return [
      color
        .match(/(\d+),\s*(\d+),\s*(\d+)/)
        .slice(1)
        // eslint-disable-next-line no-bitwise
        .map((x, i) => +x << (8 * (2 - i)))
        .reduce((x, dec) => dec + x, 0),
      defaultAlpha,
    ];
  }

  // Hexadecimal number, e.g., `0xff0000`
  return [parseInt(color, 10), defaultAlpha];
};

export default colorToDecAlpha;