fenzhi-utils/globalMethods/CustomPublic/CustomGradientColors.js

分值前端项目的js函数库

// convert #hex notation to rgb array
var parseColor = function (hexStr) {
  return hexStr.length === 4
    ? hexStr
        .substr(1)
        .split('')
        .map(function (s) {
          return 0x11 * parseInt(s, 16);
        })
    : [hexStr.substr(1, 2), hexStr.substr(3, 2), hexStr.substr(5, 2)].map(
        function (s) {
          return parseInt(s, 16);
        }
      );
};
var pad = function (s) {
  return s.length === 1 ? '0' + s : s;
};

/**
 * 渐变色数组
 * @param {string} start 开始颜色(16进制)
 * @param {string} end 结束颜色(16进制)
 * @param {number} steps 分解次数
 * @param {number} gamma  透明度
 * @returns {array} 颜色的渐变色数组
 */
/**
CustomGradientColors('#00ff00', '#ff0000', 0); // []
CustomGradientColors('#00ff00', '#ff0000', 1); // ['#00ff00']
CustomGradientColors('#00ff00', '#ff0000', 4); // ['#00ff00', '#55aa00', '#aa5500', '#ff0000']
CustomGradientColors('#000', '#fff', 3, 2.2); // ['#000000', '#bababa', '#ffffff']
 */
export function CustomGradientColors(start, end, steps, gamma) {
  if (steps === 0) {
    return [];
  } else if (steps === 1) {
    return [start];
  }
  var i,
    j,
    ms,
    me,
    output = [],
    so = [];
  gamma = gamma || 1;
  var normalize = function (channel) {
    return Math.pow(channel / 255, gamma);
  };
  start = parseColor(start).map(normalize);
  end = parseColor(end).map(normalize);
  for (i = 0; i < steps; i++) {
    ms = i / (steps - 1);
    me = 1 - ms;
    for (j = 0; j < 3; j++) {
      so[j] = pad(
        Math.round(
          Math.pow(start[j] * me + end[j] * ms, 1 / gamma) * 255
        ).toString(16)
      );
    }
    output.push('#' + so.join(''));
  }
  return output;
}