Use in Pure Node Js Script

[wordjelly]

Hi,
I wanted to use this in a pure node js script, without involving a browser in any way.
I tried the following :

const { createCanvas, loadImage } = require('canvas');
const Granim = require('granim');

function generateGradient(title, subtitle, callback) {
  const canvasWidth = 400;
  const canvasHeight = 400;

  const canvas = createCanvas(canvasWidth, canvasHeight);
  console.log(canvas);
  const ctx = canvas.getContext('2d');
  console.log(ctx);
  
  const granimInstance = new Granim({
    element: canvas,
    name: 'basic-gradient',
    direction: 'left-right',
    opacity: [1, 1],
    isPausedWhenNotInView: true,
    states: {
      "default-state": {
        gradients: [
          ['#834D9B', '#D04ED6'],
          ['#1CD8D2', '#93EDC7'],
          ['#FD4688', '#B41D52']
        ],
        transitionSpeed: 7000
      }
    }
  });

  granimInstance.events.add('endGradient', () => {
    const fileName = `gradient_${Date.now()}.png`;
    const outputPath = path.join(__dirname, fileName);

    const out = require('fs').createWriteStream(outputPath);
    const stream = canvas.createPNGStream();
    stream.pipe(out);

    out.on('finish', () => {
      callback(null, fileName);
    });

    out.on('error', (err) => {
      callback(err, null);
    });
  });
}

module.exports = generateGradient;

generateGradient("dog","cat");

This fails as it seems that Granim is looking for the class HTMLCanvasElement to be defined in the global namespace

ReferenceError: HTMLCanvasElement is not defined
    at Granim.module.exports [as getElement] (/.../node_modules/granim/lib/getElement.js:4:25)

How do you get this to work? I tried refactoring that to not look for the HTMLCanvasElement, but there are references all over the codebase to things like "window" and other browser specific javascript functions/namespaces.

Is there any way to make this library work in a pure node js script?

Thanks.