Sharing image generated from html canvas on FB - facebook-javascript-sdk

Question

This one I've been banging my head against for a few weeks now.
Scenario:
Let user generate an image out of layers they select
Convert image to canvas
Share image from canvas on facebook wall using share_open_graph (along with the image, a short text and title will be shared)
I've already had a solution in place using publish_actions but that was recently removed from the API and is no longer available.
I am using js and html for all code handling.
The issue is that I can generate a png image from the canvas but that is saved as base64 and share_open_graph doesn't allow this type of image, it needs a straight forward url such as './example.png'. I have tried using several approaches and with canvas2image, converting and saving image using file-system but all of these fail.
Does anyone have similar scenario and possible solution from April/May 2018 using share_open_graph ?
My current code looks like this - it fails at the image conversion and save to a file (Uncaught (in promise) TypeError: r.existsSync is not a function at n (file-system.js:30)). But I am open to different solutions as this is clearly not working.
html2canvas(original, { width: 1200, height: 628
}).then(function(canvas)
{
fb_image(canvas);
});
var fb_image = function(canvas) {
canvas.setAttribute('id', 'canvas-to-share');
document.getElementById('img-to-share').append(canvas);
fbGenerate.style.display = 'none';
fbPost.style.display = 'block';
var canvas = document.getElementById('canvas-to-share');
var data = canvas.toDataURL('image/png');
var encodedPng = data.substring(data.indexOf(',') + 1, data.length);
var decodedPng = base64.decode(encodedPng);
const buffer = new Buffer(data.split(/,\s*/)[1], 'base64');
pngToJpeg({ quality: 90 })(buffer).then(output =>
fs.writeFile('./image-to-fb.jpeg', output));
var infoText_content = document.createTextNode('Your image is being
posted to facebook...');
infoText.appendChild(infoText_content);
// Posting png from imageToShare to facebook
fbPost.addEventListener('click', function(eve) {
FB.ui(
{
method: 'share_open_graph',
action_type: 'og.shares',
href: 'https:example.com',
action_properties: JSON.stringify({
object: {
'og:url': 'https://example.com',
'og:title': 'My shared image',
'og:description': 'Hey I am sharing on fb!',
'og:image': './image-to-fb.jpeg',
},
}),
},
function(response) {
console.log(response);
}
);
});
};