ColorScale.prototype.setNormalizeFunction = function (f) {
  if (f === 'polynomial') {
    this.normalize = function (value) {
      return Math.pow(value, 0.2);
    };
  } else if (f === 'linear') {
    delete this.normalize;
  } else {
    this.normalize = f;
  }
  this.setMin(this.clearMinValue);
  this.setMax(this.clearMaxValue);
};