I am using a Google Script to generate tickets to an event, and the ticket includes a QR code which goes to a pre-filled Google Form link. Since it's pre-filled, the string is quite long, and the Google Charts API for creating QR codes will not accept a string of text that long using a GET request, but I can't find any documentation of how to code the POST request into Apps Script. How do I generate a POST request in Apps Script that will return an image of the QR code which I can then insert into the document?
I already tried the GET request, and it truncates the URL before encoding it into a QR code. That gets me to the Google Form, but not the pre-filled version that the link generates (actually pretty smart on Google's part to have it truncate the string in a place that still gives a usable URL, but that's for another day...)
I have also tried the HtmlService to render the QR code using the POST method with the Charts API in an HTML form that automatically submits on the loading of that HTML. If I use showSidebar(), this will open the image in a new tab, but I haven't figured out how to return that image so that it can be inserted into the document.
I've also tried creating a blob with the HTML and then saving the blob as a PNG, but from the research I've done, the .getAs() method doesn't render images when converting the HTML.
The renderQR function:
function renderQR(inputUrl) {
var html = HtmlService.createTemplateFromFile('QREncode.html');
html.url = inputUrl;
var rendered = html.evaluate().setSandboxMode(HtmlService.SandboxMode.IFRAME)
.setHeight(300)
.setWidth(300);
return rendered;
}
The QREncode.html file:
<!DOCTYPE html>
<html>
<head>
<base target="_top">
<script type='application/javascript'>
// Send the POST when the page is loaded,
// which will replace this whole page with the retrieved chart.
function loadGraph() {
var frm = document.getElementById('post_form');
if (frm) {
frm.submit();
}
}
</script>
</head>
<body onload="loadGraph()">
<form action='https://chart.googleapis.com/chart' method='POST' id='post_form'>
<input type='hidden' name='cht' value='qr' />
<input type='hidden' name='chl' value='<?= url ?>' />
<input type='hidden' name='chs' value='300x300' />
<input type='submit'/>
</form>
</body>
</html>
When I treat the return from the renderQR() function as an image, Apps script gives an error saying that it is "Invalid image data", which makes sense -- but how do I convert it into an image, or is there a better or simpler way I could be doing this?
You need to get the qr code in the Apps Script, not in the browser:
var imageData = UrlFetchApp.fetch('https://chart.googleapis.com/chart', {
'method' : 'post',
'payload' : {
'cht': 'qr',
'chl': 'https://google.com',
'chs': '300x300'
}}).getContent();