@elastic/eui/es/services/color/contrast.js

Elastic UI Component Library

function _typeof(o) { "@babel/helpers - typeof"; return _typeof = "function" == typeof Symbol && "symbol" == typeof Symbol.iterator ? function (o) { return typeof o; } : function (o) { return o && "function" == typeof Symbol && o.constructor === Symbol && o !== Symbol.prototype ? "symbol" : typeof o; }, _typeof(o); }
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

import chroma from 'chroma-js';
import { shade, tint, lightness as getLightness } from './manipulation';
import { getOn } from '../theme/utils';
export var getColorContrast = function getColorContrast(textColor, backgroundColor) {
  return chroma.contrast(textColor, backgroundColor);
};
export var wcagContrastMin = 4.5; // WCAG AA minimum contrast ratio for normal (non-large) text

/**
 * Creates a new color that meets or exceeds WCAG level AA
 * @param foreground - Color to manipulate
 * @param ratio - Amount to change in absolute terms. 0-10.
 * *
 * @param themeOrBackground - Color to use as the contrast basis or just pass EuiTheme
 */
export var makeHighContrastColor = function makeHighContrastColor(_foreground) {
  var ratio = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 4.85;
  return function (themeOrBackground) {
    var _getOn;
    var foreground = _typeof(themeOrBackground) === 'object' ? (_getOn = getOn(themeOrBackground, _foreground)) !== null && _getOn !== void 0 ? _getOn : _foreground : _foreground;
    var background = _typeof(themeOrBackground) === 'object' ? themeOrBackground.colors.body : themeOrBackground;
    if (chroma(foreground).alpha() < 1 || chroma(background).alpha() < 1) {
      console.warn("Contrast cannot be accurately calculated when colors have alpha channel opacity. Make sure the provided foreground and background colors have no transparency:\n\nForeground: ".concat(foreground, "\nBackground: ").concat(background));
    }
    var contrast = chroma.contrast(foreground, background);

    // Determine the lightness factor of the background color first to
    // determine whether to shade or tint the foreground.
    var brightness = getLightness(background);
    var highContrastTextColor = foreground;
    while (contrast < ratio) {
      if (brightness > 50) {
        highContrastTextColor = shade(highContrastTextColor, 0.05);
      } else {
        highContrastTextColor = tint(highContrastTextColor, 0.05);
      }
      contrast = chroma.contrast(highContrastTextColor, background);
      var lightness = getLightness(highContrastTextColor);
      if (lightness < 5) {
        console.warn('High enough contrast could not be determined. Most likely your background color does not adjust for light mode.');
        return highContrastTextColor;
      }
      if (lightness > 95) {
        console.warn('High enough contrast could not be determined. Most likely your background color does not adjust for dark mode.');
        return highContrastTextColor;
      }
    }
    return chroma(highContrastTextColor).hex();
  };
};

/**
 * Creates a new color with increased contrast
 * Disabled content only needs a contrast of at least 2 because there is no interaction available
 * @param foreground - Color to manipulate
 * @param ratio - Amount to change in absolute terms. 0-10.
 * *
 * @param themeOrBackground - Color to use as the contrast basis
 */
export var makeDisabledContrastColor = function makeDisabledContrastColor(color) {
  var ratio = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 2;
  return function (themeOrBackground) {
    return makeHighContrastColor(color, ratio)(themeOrBackground);
  };
};
export var warnIfContrastBelowMin = function warnIfContrastBelowMin(textColor, backgroundColor) {
  var min = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : wcagContrastMin;
  var ratio = getColorContrast(textColor, backgroundColor);
  if (ratio < min) {
    // eslint-disable-next-line no-console
    console.warn("Warning: ".concat(backgroundColor, " background with ").concat(textColor, " text has a low contrast of ").concat(ratio.toFixed(2), ". Should be above ").concat(min, "."));
  }
};