1.x Lambda code


Add Lambda layer

In the Designer section, open Layers and select Add a layer.

Add Lambda layer

Choose a layer

Select Custmer layers. Select the custom Lambda layer we created in the previous step, chrome-aws-lambda Select Version 1 Select Add

Add chrome-aws-lambda custom layer

You should now see a (1) in the Lambda Layers box.

Layer added

Function code

Add function code

The Function code section includes a default function that we can modify using the built in code editor.

Replace function code

Copy and paste the code below to replace the default function.

const chromium = require('chrome-aws-lambda')
const AWS = require("aws-sdk");
const s3 = new AWS.S3();
const s3Bucket = process.env.S3_TRAINING_BUCKET

const zeroPad = (num, places) => String(num).padStart(places, '0')

exports.handler = async (event, context, callback) => {
  let result = null
  let browser = null
  let results = []
  try {
    browser = await chromium.puppeteer.launch({
      args: chromium.args,
      defaultViewport: chromium.defaultViewport,
      executablePath: await chromium.executablePath,
      headless: chromium.headless,
      ignoreHTTPSErrors: true,
    let page = await browser.newPage();
    for (let i = 0; i < 231; i++) {
        let bp = zeroPad(i, 4);
        const url = 'https://aws-computer-vision.jacobcantwell.com/gauge/?bp=' + bp;
        const s3Key = 'training-images/pressure-gauge-bp-'+bp+'.jpg';
        await page.setViewport({ width: 700, height: 780 });
        await page.goto(url);
        const screenshot = await page.screenshot({
            type: 'jpeg',
            fullPage: true
        const s3Params = {
            Bucket: s3Bucket,
            Key: s3Key,
            Body: screenshot
        await s3.putObject(s3Params).promise();
        console.log('finished screenshot', s3Key);
    result = {
        urls: results
} catch (error) {
    return callback(error);
  } finally {
    if (browser !== null) {
      await browser.close();
  return callback(null, result);

Select the Deploy button.

New function code

Environment variables

  • Select Edit
  • Select Add environment variable
  • Enter a Key/Value pair for the S3 training bucket
    • Key enter S3_TRAINING_BUCKET
    • Value enter analogue-gauge-images-158287123688
  • Select Save

Environment variables

Select the Deploy button. You should see a message Your changes have been saved..

Basic settings

The Memory (MB) setting determines the amount of memory available for your Lambda function during invocation.

The default Timeout setting is 3 seconds. If tested now, the Lambda will throw an error message saying the task timed out after 3 seconds. Each screenshot takes up to 3 seconds to generate, we will create 230 images, so the timeout needs to be more than 690 seconds.

  • Edit the Description - Add a description of the function, This function creates the training data for the Read Analogue Gauges workshop.
  • Memory (MB) - Increase to 4096 MB
  • Timeout - Increase to 15 min
  • Execution role - Select the existing service role with the service-role/captureAnalogueGaugeBuilder-role- prefix
  • Select Save

Basic settings

Select the Deploy button. You should see a message Your changes have been saved..


Change to the Permissions tab at the top of the Lambda function page.

Execution role

Select the role name with the captureAnalogueGaugeBuilder-role- prefix. This will launch the Identity and Access Management (IAM) service in a new tab.

Edit execution role

  • Select Attach policies
  • Filter the policies with S3
  • Select AmazonS3FullAccess
  • Select Attach policy

Security best practices are to give resources only the absolute minumum permissions so that they can function. Instead of a general AWS managed policy, you can create a custom IAM policy that only grants write access to the single S3 training bucket.

Return back to the lambda function tab in your web browser.


  • Select Test at the top of the Lambda function page.


  • Enter an Event name captureGaugeBuilder
  • Leave the test event JSON at its default value
  • Select Create


You should now see a new captureAnalogueGauges test event next to the Test button. Select Test.

An Executing function… message will appear and the Lambda function should run for several minutes while it generates the training images.

Test running


You can see the progress of the training image generation by browsing to the S3 bucket.

  • Search for S3 in the AWS Management Console search bar
  • Open the analogue-gauge-images- prefixed training bucket
  • Open the training-images folder

Select the Refresh button to see more Objects as they are created. When the Lambda function is complete 231 training images will be created.

S3 bucket view

  • Select one of the training images
  • Select Object actions then Download to download a training image to your local computer

S3 object view

The image will download to your local computer for you to preview.

Pressure gauge image

Pressure gauge image

Pressure gauge image