如何从google charteditor打印png图表？

<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>

<div id="chart_div"></div>

google.charts.load('current', {packages: ['corechart']});

google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', 'Expenses'],
    ['2015', 1000, 400],
    ['2016', 1170, 460],
    ['2017', 660, 1120],
    ['2018', 1030, 540]
  ]);

  var options = {
    title: 'Company Performance',
    width: 400,
    height: 300
  };

  var chart = new google.visualization.ColumnChart(document.getElementById('chart_div'));
  chart.draw(data, options);
}

var chart_div = document.getElementById('chart_div');
var chartImageURL = chart_div.getElementsByTagName('img')[0].src;