AWS Lambda Image Resizer using Node.js

An AWS Lambda Function to resize S3 images using Node.js on the fly.

A detailed, screenshot-ed, step-by-step guide can be found here.

How Do Images Get Resized?

1. User requests an image from the API Gateway.
2. API Gateway triggers the Lambda Function.
3. Lambda function runs basic validations on user input.
4. The function checks if a resized image exists on S3 Bucket.
5. If a resized image exists, image is returned as a response to the API Gateway.
6. If no resized image found, a new resized version is created on the fly and saved to S3 Bucket.
7. Resized image is returned as a response to the API Gateway.

AWS Services Used

• AWS Lambda
• Amazon API Gateway
• Amazon S3
• AWS IAM
• (Optional) Amazon Cloud Watch

Prerequisites

• AWS Console root access.
• OR, AWS Console full access to the four AWS Services above.

Setup

1. Setup S3 Bucket.

   • Open AWS Console and go to S3 Home.
   • Click on Create bucket button.
   • Choose a name and a region for your new bucket.
   • Keep a note of the bucket name, we will need it later.
   • Click on Create bucket.

2. Setup IAM Role.

   • Go to IAM Home, then under Access management click on Roles.
   • Click on Create role button.
   • Under Select type of trusted entity select AWS Service (EC2, Lambda and others).
   • Under Choose a use case select Lambda.
   • Click on Next: Permissions.
   • Click on Create policy.
   • Switch to JSON tab, then copy and paste the below.

   {
       "Version": "2012-10-17",
       "Statement": [
           {
               "Effect": "Allow",
               "Resource": "arn:aws:s3:::YOUR_S3_BUCKET_NAME/*",
               "Action": [
                   "s3:GetObject",
                   "s3:PutObject"
               ]
           }
       ]
   }

   • Don't forget to replace YOUR_S3_BUCKET_NAME with your created S3 Bucket Name.
   • Click on Next: Tags.
   • Click on Next: Review.
   • Click on Review policy.
   • Set a name for the new policy and click Create policy.
   • Go back to Create IAM Role page, hit the refresh button, search for and select the policy you just created.
   • Click on Next: Tags.
   • Click on Next: Review.
   • Enter a name for the new role and click Create role.
   • (Optional) if you would like to log API Gateway calls to Amazon Cloudwatch
     • Click to edit the role you just created.
     • Click on Attach policies.
     • Type and select AmazonAPIGatewayPushToCloudWatchLogs from the Filter policies search box.
     • Click Attach policy.

3. Setup Lambda Function

   • Go to Lambda Home.
   • Click on Create function.
   • Under Choose one of the following options to create your function choose Author from scratch.
   • For Runtime, choose Node.js 18.x.
   • Under permissions, choose Use an existing role, then from roles list select the role you just created.
   • Click on Create function.
   • Under Function code section, click to expand Actions dropdown the click Upload a .zip file.
   • Download the Build file and upload it as your Lambda function source code.
   • Under Environment variables section, click Edit.
   • Click Add environment variable.
   • For Key type BUCKET and for Value paste in YOUR_S3_BUCKET_NAME.
   • (Optional) If you would like to restrict resizing images to predefined dimensions, click Add environment variable.
     • For Key type WHITELISTED_DIMENSIONS and for Value type your predefined dimensions separated by a space, for example 320x280 640x480 1200x800.
   • Click Save.

4. Setup API Gateway

   • Go to API-Gateway APIs.
   • Under Choose an API type spot HTTP API block and click on Build.
   • Type your API name under API name.
   • Click on Review and Create. (don't worry, you will come back later)
   • Click on Create.
   • From the menu on the left, under Develop, click on Routes.
   • Click on Create button.
   • For Method choose GET and for Route Path /{proxy+}.
   • Click on Create.
   • Now you should see the route you created under Routes Block. Click on the Method you just created GET.
   • Route details should show, click on Attach integration.
   • Click on Create and attach integration.
   • Under Integration target, Integration type select Lambda function.
   • Under Integration details, Integration target select your Lambda function region under AWS Region and your Lambda function under Lambda function.
   • Click on Create.
   • From the menu on the left, under Deploy, click on Stages.
   • Click on Create.
   • Under Stage details, enter a stage name. For example production.
   • Click on Create.
   • Click on Deploy button on the top right.
   • Select the stage you just created from under Select a stage.
   • Click on Deploy to stage.
   • API URL should now appear under Invoke URL. Copy it as that's the URL to be used to resize images.

5. Finally, resize images using AWS Lambda!

   • Resized image URL structure:

   # Resize using Width and Height.
   
   {api_gatewau_url}/{width}x{height}/{s3_object_path}
   # example: https://dh12oluo25.execute-api.us-east-1.amazonaws.com/production/180x120/image.png
   # example: https://dh12oluo25.execute-api.us-east-1.amazonaws.com/production/640x480/path/to/image.jpeg
   

   OR

   # Resize using Width, Height and Fit.
   
   {api_gatewau_url}/{width}x{height}_{fit}/{s3_object_path}
   # example: https://dh12oluo25.execute-api.us-east-1.amazonaws.com/production/180x120_fill/image.png
   # example: https://dh12oluo25.execute-api.us-east-1.amazonaws.com/production/640x480_inside/another/path/to/image.jpg
   

   • URL variables explained:
     • {api_gateway_url}: The API Gateway URL. Example https://dh12oluo25.execute-api.us-east-1.amazonaws.com/production.
     • {width}: Image width in pixels or 'auto'.
     • {height}: Image height in pixels or 'auto'.
     • {fit}: Sharp.js image fit. Defaults to 'cover'.
     • {s3_object_path}: Path to image inside S3 Bucket.

Build Your Own AWS Lambda Image Resizer

Because requirements always differ and there's no one magic size fits all, this simple resizer is designed so you can modify the original script to match your requirements and then rebuild it in order to be published to your own AWS Lambda Function.

This resizer is making use of Sharp to resize images. A build script is included in the package.json file which makes sure that the Sharp linux binaries are added to package.

Run the build script after making your changes to index.js, you will find a new zip file in /app/dist when in runs successfully.

npm run build

A docker file is included for testing purposes. See the amazon documentation on how to test your function.

1. Download and install Docker and Docker Compose.

2. After making a change to the string, rerun the docker compose command.

docker compose up --build

7. Press ctrl+c to kill the running container.

8. Upload .zip build file to your AWS Lambda function.

Documentation

Here

Issues and feature requests

Here

License

MIT

Credits

• SagidM's s3-resizer.