Save charts on server - symfony

Question

I have a symfony3 project with working Highcharts functions implemented through the ob/highcharts-bundle and I really like the way the generated charts look with a custom theme.
I would like to be able to run a script on the server that generates an email and along the way builds the charts that I need (complete with my custom theme) and saves to the server so I can link to them from the email.
I've previously done this in pChart, and saving an image on the server from a script is as easy as $myPicture->autoOutput('myimage.png'). While that's easy, I prefer the look of charts from Highcharts.
Is there a similar simple way to do this something like this using Highcharts?
My scripts look like this:
// Controller
$xdata = array(1, 2, 3, 4);
$data_series = array(
0 => array(
"name" => "Series 1",
"data" => array(
0 => 2.0, 1 => 0.0, 2 => 5.0, 3 => 2.3, 4 => 0.45, 5 => 0.4
)
)
);
$ob = new Highchart();
$ob->chart->renderTo('trendchart'); // id of the div where the chart gets rendered
$ob->title->text('Chart title');
$ob->xAxis->categories($xdata);
$ob->series($data_series);
return $this->render('dashboard/main.html.twig', [
'trendChart' => $ob,
]);
and I render this in a twig template:
// twig template
{% extends 'base.html.twig' %}
{% block javascripts %}
{{ parent() }}
<script src="//code.highcharts.com/highcharts.js"></script>
<script src="//code.highcharts.com/modules/exporting.js"></script>
<script src="{{ asset('js/highchartThemes/mytheme.js') }}"></script>
<script>
{{ chart(trendChart) }}
</script>
{% endblock %}
{% block body %}
<div id="trendchart"></div>
{% endblock %}
What I'm hoping for is to make a call from my controller like:
$ob->save('myimage.png');
Does anyone know of a simple/clean way to do something like this?