Firebase cloud functions image proxy server. I use it to overcome Flutter CORS issues with the images. ie. CORS Proxy server

Firebase cloud functions CORS image proxy.js

const cors = require('cors')({ origin: true });

const request = require('request');

functions.https.onRequest((req, res) {
  cors(req, res, () => {
    let url = req.query.url;

    if (!url) {
      url = req.body.url;
    }

    if (!url) {
      res.status(403).send('URL is empty.');
    }

    return request.get(url).pipe(res);
  });
})

Make sure you have installed cors and request package.
e.g

npm install cors request --save