Node script to screenshot web pages using chrome debugging protocol

chrome_screenshot.js

// npm install chrome-remote-interface minimist
const CDP = require('chrome-remote-interface');
const argv = require('minimist')(process.argv.slice(2));
const file = require('fs');
const spawn = require('child_process').spawn;
const net = require('net');
const crypto = require('crypto');

const url = argv.url || 'https://www.google.com';
const id = argv.id || crypto.createHash('sha256').update(url).digest("hex");
const viewportWidth = argv.viewportWidth || 1440;
const viewportHeight = argv.viewportHeight || 900;
const delay = argv.delay || 200;
const debugport = argv.port || 9222

// Reference: https://www.npmjs.com/package/wait-for-port
function wait_for_port(host, port, cb) {
  var retriesRemaining = 10;
  var retryInterval = 200;
  var timer = null, socket = null;

  function clearTimerAndDestroySocket() {
    clearTimeout(timer);
    timer = null;
    if (socket) socket.destroy();
    socket = null;
  }

  function tryToConnect() {
    clearTimerAndDestroySocket();
    if (--retriesRemaining < 0) return cb(new Error('out of retries'));

    socket = net.createConnection(port, host, function(err) {
      clearTimerAndDestroySocket();
      if (retriesRemaining > 0) cb(null);
    });

    timer = setTimeout(tryToConnect, retryInterval);
    socket.on('error', function(err) {
      clearTimerAndDestroySocket();
      setTimeout(tryToConnect, retryInterval);
    });
  }

  tryToConnect();
};

console.log("Launching chrome");
// WARN: Using no-sandbox to run nicely inside docker for now
const chrome_args = ["--headless", "--hide-scrollbars", `--remote-debugging-port=${debugport}`, "--disable-gpu", "--no-sandbox"];
console.log(chrome_args);
const proc = spawn("google-chrome", chrome_args);

console.log(`Connecting to debug port on 127.0.0.1:${debugport}`);
wait_for_port("127.0.0.1", debugport, (err) => {
  if (err) {
    console.log("Unable to connect to chrome debug port, exiting");
    process.exit(2);
  }

  // Reference: https://medium.com/@dschnr/using-headless-chrome-as-an-automated-screenshot-tool-4b07dffba79a
  CDP(function(client) {
    const {Emulation, Page, Security} = client;

    Page.loadEventFired(() => {
      console.log("Page loaded");
      setTimeout(() => {
        console.log("Taking screenshot");
        Page.captureScreenshot({format : 'png'}, (err, screenshot) => {
          if (!err) {
            const buffer = new Buffer(screenshot.data, 'base64');
            file.writeFileSync(`${id}_screenshot.png`, buffer, 'base64');
          }
          client.close();
          process.exit(0);
        });
      }, delay);
    });

    // Reference: https://github.com/cyrus-and/chrome-remote-interface/wiki/Bypass-certificate-errors-(%22Your-connection-is-not-private%22)
    Security.certificateError(({eventId}) => {
      Security.handleCertificateError({
        eventId,
        action: 'continue'
      });
    });

    const deviceMetrics = {
      width: viewportWidth,
      height: viewportHeight,
      deviceScaleFactor: 0,
      mobile: false,
      fitWindow: false,
    };

    Promise.all([
      Page.enable(),
    ]).then(() => {
      console.log("Configuring browser");
      return Promise.all([
        Emulation.setDeviceMetricsOverride(deviceMetrics),
        Emulation.setVisibleSize({width: viewportWidth, height: viewportHeight}),
        Security.enable(),
        Security.setOverrideCertificateErrors({override: true})
      ]);
    }).then(() => {
      console.log("Navigating to page ", url);
      return Page.navigate({url});
    })

    setTimeout(() => {
      console.log("Timeout loading page, exiting");
      client.close();
      process.exit(3);
    }, delay + 5000);

  }).on('error', err => {
    console.error('Cannot connect to browser:', err);
    process.exit(4);
  });
});