AWS Lambda function to create multiple thumbnails

This code creates multiple thumbnails with AWS lambda feature using node.js (v0.10.42) and Imagemagick library.

This example doesn't use any external npm packages (even imagemagicwrapper) as recommended here http://docs.aws.amazon.com/lambda/latest/dg/with-s3-example-deployment-pkg.html

Introduction

When you or your app uploads image on S3 bucket, this code downloads image, makes thumbnails with command like this:

convert FILENAME \( +clone -quality 80 -interlace Plane -resize 264x177\> -write jpeg:- +delete \)
   \( +clone -quality 80 -interlace Plane -resize 576x387\> -write jpeg:- +delete \)
   \( +clone -quality 80 -interlace Plane -resize 1242x834\> -write jpeg:- +delete \)
   \( +clone -quality 80 -interlace Plane -resize 5000x5000\> -write jpeg:- +delete \)
   null:

then grabs binary stdout buffer, splits buffer into images, puts images back to S3, notifies you backend via Amazon SNS and optionaly removes the original file

Installation

1. Create lambda function https://console.aws.amazon.com/lambda/home?region=us-east-1#/functions
2. Enter any name you want
3. Select runtime Node.js 0.10 (4.3 needs some refactor)
4. Copy code from resizer.js to inline textarea or upload package (see https://docs.aws.amazon.com/console/lambda/nodejsdeploy)
5. Set handler value exports.resizer
6. Select Role for lambda execution (or create new Basic execution role)
7. If you want to upload or delete files with this lambda add policy to execution role:

{
    "Action": [
        "s3:DeleteObject",
        "s3:PutObject",
        "s3:PutObjectAcl"
    ],
    "Effect": "Allow",
    "Resource": "arn:aws:s3:::*"
}

8. I recommend to change memory limit to 512 MB and timeout to 15 seconds (depends on input/output image sizes)
9. Add event handler for your bucket for necessary input (e.g. input/images) and/or extensions (*.jpg, *.png)

Usage

You can modify code for you needs. Adjust thumbnail sizes, prefixes, SNS ARN topics (getTopicArn function) if you use SNS service