Printing PNG Charts

Overview
Snapshotting Selections

Overview

Google Charts can be printed directly from your browser, or from JavaScript via the print() function. If you want to provide access to a PNG image of a chart, you can use the getImageURI() method. This currently works for core charts and geocharts.

If your chart (of type ChartType, such as ColumnChart or PieChart) is called my_chart and the div displaying it is my_div, here's how you access the chart as a PNG:

    var my_div = document.getElementById('chart_div');
    var my_chart = new google.visualization.ChartType(chart_div);

    google.visualization.events.addListener(my_chart, 'ready', function () {
      my_div.innerHTML = '<img src="' + my_chart.getImageURI() + '">';
    });

    my_chart.draw(data);

Note: You should wait for the ready event, as shown in the examples on this page, to ensure that the chart has finished rendering.

Note: This will only work in browsers that support the HTML5 <canvas> element, and so won't work on Internet Explorer 9 or earlier.

Here's a complete example:

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

  <script type="text/javascript">
    google.charts.load("current", {packages:['corechart']});
    google.charts.setOnLoadCallback(drawChart);
    function drawChart() {

      var data = google.visualization.arrayToDataTable([
        ['Element', 'Density', { role: 'style' }],
        ['Copper', 8.94, '#b87333', ],
        ['Silver', 10.49, 'silver'],
        ['Gold', 19.30, 'gold'],
        ['Platinum', 21.45, 'color: #e5e4e2' ]
      ]);

      var options = {
        title: "Density of Precious Metals, in g/cm^3",
        bar: {groupWidth: '95%'},
        legend: 'none',
      };

      var chart_div = document.getElementById('chart_div');
      var chart = new google.visualization.ColumnChart(chart_div);

      // Wait for the chart to finish drawing before calling the getImageURI() method.
      google.visualization.events.addListener(chart, 'ready', function () {
        chart_div.innerHTML = '<img src="' + chart.getImageURI() + '">';
        console.log(chart_div.innerHTML);
      });

      chart.draw(data, options);

  }
  </script>

<div id='chart_div'></div>

When this program runs, chart_div.innerHTML will be set to this PNG encoding of the chart and displayed in the JavaScript console:

data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAADICAYAAADGFbfiA...

When that URI is placed directly into a browser address bar, modern browsers will render the image:

You can include a link to the printable version with the following line of JavaScript:

  document.getElementById('png').outerHTML = '<a href="' + chart.getImageURI() + '">Printable version</a>';

followed by this line in your HTML:

  <div id='png'></div>

Snapshotting Selections

As a chart creator, you can do most anything to your charts programmatically that users can do in their browsers. So if you want to create a static image of the chart with a tooltip showing or with crosshairs at a particular point, you can do that by calling setSelection() prior to getImageURI(), as shown below.

Here's a scatter chart with 100 random points, one of them with tooltip and crosshairs pre-selected:

Reload and you'll see a different point selected. The code, with key lines in bold:

<script type="text/javascript">
  google.charts.load("current", {packages:['corechart']});
  google.charts.setOnLoadCallback(drawChart);
  function drawChart() {
    var data = new google.visualization.DataTable();
    data.addColumn('number');
    data.addColumn('number');
    for (var i = 0; i < 100; i++)
      data.addRow([Math.floor(Math.random() * 100),
                   Math.floor(Math.random() * 100)]);

    var options = {
      legend: 'none',
      crosshair: { trigger: 'both' },   // Display crosshairs.
      tooltip: { trigger: 'selection' } // Display tooltips on selection.
    };

    var chart = new google.visualization.ScatterChart(document.getElementById('scatter_setselection'));

    google.visualization.events.addListener(chart, 'ready', function () {
      chart.setSelection([{row:99, column:1}]); // Select one of the points.
      png = '<a href="' + chart.getImageURI() + '">Printable version</a>';
      console.log(png);
    });

    chart.draw(data, options);
  }