code: function Heatmap() {
      var canvas = zrUtil.createCanvas();
      this.canvas = canvas;
  
      this.blurSize = 30;
      this.pointSize = 20;
  
      this.maxOpacity = 1;
      this.minOpacity = 0;
  
      this._gradientPixels = {};
  }
docs: Heatmap Chart
  
  @class