Export Highcharts to PDF (using javascript and local server - no internet connection)

Question

I am using Highcharts in my application (without any internet connection)

I have multiple charts on a html page, and I want to generate a PDF report that contains all the charts from this page.

How can I do this without sending the data to any server on the internet ?

I will be thankful for any help or any example you can provide. Thank you in advance :)

Answer 1

Yes this is possible but involves a few different libraries to get working. The first Library is jsPDF which allows the creation of PDF in the browser. The second is canvg which allows for the rendering and parsing of SVG's, the bit that is really cool though is it can render an svg on to canvas element. Lastly is Highcharts export module which will allow us to send the svg to the canvg to turn into a data URL which can then be given to jsPDF to turn into your pdf.

Here is an example http://fiddle.jshell.net/leighking2/dct9tfvn/ you can also see in there source files you will need to include in your project.

So to start highcharts provides an example of using canvg with it's export to save a chart as a png. because you want all the iamges in a pdf this has been slightly altered for our purpose to just return the data url

// create canvas function from highcharts example http://jsfiddle.net/highcharts/PDnmQ/
(function (H) {
    H.Chart.prototype.createCanvas = function (divId) {
        var svg = this.getSVG(),
            width = parseInt(svg.match(/width="([0-9]+)"/)[1]),
            height = parseInt(svg.match(/height="([0-9]+)"/)[1]),
            canvas = document.createElement('canvas');

        canvas.setAttribute('width', width);
        canvas.setAttribute('height', height);

        if (canvas.getContext && canvas.getContext('2d')) {

            canvg(canvas, svg);

            return canvas.toDataURL("image/jpeg");

        }?
        else {
            alert("Your browser doesn't support this feature, please use a modern browser");
            return false;
        }

    }
}(Highcharts));

Then for the example i have set up export on a button click. This will look for all elements of a certain class (so choose one to add to all of your chart elements) and then call their highcharts.createCanvas function.

$('#export_all').click(function () {
    var doc = new jsPDF();

    // chart height defined here so each chart can be palced
    // in a different position
    var chartHeight = 80;

    // All units are in the set measurement for the document
    // This can be changed to "pt" (points), "mm" (Default), "cm", "in"
    doc.setFontSize(40);
    doc.text(35, 25, "My Exported Charts");

    //loop through each chart
    $('.myChart').each(function (index) {
        var imageData = $(this).highcharts().createCanvas();

        // add image to doc, if you have lots of charts,
        // you will need to check if you have gone bigger 
        // than a page and do doc.addPage() before adding 
        // another image.

        /**
        * addImage(imagedata, type, x, y, width, height)
        */
        doc.addImage(imageData, 'JPEG', 45, (index * chartHeight) + 40, 120, chartHeight);
    });


    //save with name
    doc.save('demo.pdf');
});

important to note here that if you have lots of charts you will need to handle placing them on a new page. The documentation for jsPDF looks really outdated (they do have a good demos page though just not a lot to explain all the options possible), there is an addPage() function and then you can just play with widths and heights until you find something that works.

the last part is to just setup the graphs with an extra option to not display the export button on each graph that would normally display.

//charts
$('#chart1').highcharts({
    navigation: {
            buttonOptions: {
                enabled: false
            }
        },

//this is just normal highcharts setup form here for two graphs see fiddle for full details

The result isn't too bad i'm impressed with the quality of the graphs as I wasn't expecting much from this, with some playing of the pdf positions and sizes could look really good.

Here is a screen shot showing the network requests made before and after the export, when the export is made no requests are made http://i.imgur.com/ppML6Gk.jpg

here is an example of what the pdf looks like http://i.imgur.com/6fQxLZf.png (looks better when view as actual pdf)

quick example to be tried on local https://github.com/leighquince/HighChartLocalExport