checktheroads-hyperglass/hyperglass/ui/util.js

import chroma from "chroma-js";

const isDark = color => {
  // YIQ equation from http://24ways.org/2010/calculating-color-contrast
  const rgb = chroma(color).rgb();
  const yiq = (rgb[0] * 299 + rgb[1] * 587 + rgb[2] * 114) / 1000;
  return yiq < 128;
};

const isLight = color => isDark(color);

const opposingColor = (theme, color) => {
  if (color.match(/^\w+\.\d+$/m)) {
    const colorParts = color.split(".");
    if (colorParts.length !== 2) {
      throw Error(`Color is improperly formatted. Got '${color}'`);
    }
    const [colorName, colorOpacity] = colorParts;
    color = theme.colors[colorName][colorOpacity];
  }
  const opposing = isDark(color) ? theme.colors.white : theme.colors.black;
  return opposing;
};

const googleFontUrl = (fontFamily, weights = [300, 400, 700]) => {
  const urlWeights = weights.join(",");
  const fontName = fontFamily
    .split(/, /)[0]
    .trim()
    .replace(/'|"/g, "");
  const urlFont = fontName.split(/ /).join("+");
  const urlBase = `https://fonts.googleapis.com/css?family=${urlFont}:${urlWeights}&display=swap`;
  return urlBase;
};

export { isDark, isLight, opposingColor, googleFontUrl };