Part 3 - Generating Images with Puppeteer

📅 Posted: Jun 9, 2018

Now that we’ve been able to successfully generate the HTML using JSON input, it’s time to take this generated HTML and generate an image from it using the puppeteer library.

Puppeteer will effectively allow us to run a headless version of chrome within our Node project and it will be able to load our html and render it just as a browser would before we then set about taking a screenshot.

Before we can get started implementing any new functions, let’s start by installing the puppeteer library like so:

npm install puppeteer

With this in place, let’s open up our cards.js file and start implementing the function which will take in our raw html and convert it into an image for us:

const puppeteer = require('puppeteer')

...

async function generateImage(html) {
    const browser = await puppeteer.launch({
      args: ["--no-sandbox"],
      timeout: 10000,
    });
    const page = await browser.newPage();
    await page.setContent(html)
    await page.setViewport({ width: 2048, height: 1170 });
    const screenshot = await page.screenshot({
        encoding: 'binary'
     });
    await browser.close();
    return screenshot;
}

module.exports = {
  generateHTML,
  generateImage
};

Now that we have this in place, let’s open up routes/cards.js and modify our route so that it calls our newly built generateImage function and also returns the image:

const express = require('express');
const router = express.Router()

const { generateHTML, generateImage } = require('../cards/card')

router.get('/', async (req, res) => {
    let data = {};
    let html = await generateHTML(data);
    let image = await generateImage(html);
    res.contentType('image/jpeg');
    res.end(image, 'binary');
})

module.exports = router;

Awesome, let’s open up the browser and navigate to the /card/ path to see if it all worked!

If everything has worked, you should see our newly generated image rendering within the browser! Awesome!!

The full version of the code up until this point can be found on the backend-03 branch in the repository for this course