Resizing images uploaded to Amazon S3 with AWS Lambda (Python)

Create an AWS Lambda function that resizes images uploaded to Amazon S3.

A Lambda function consumes events from an Amazon S3 bucket. The Lambda code checks the uploaded file is an image, creates a thumbnail version of the image, then uploads the thumbnail to the destination bucket.

This pattern deploys a Lambda function and two S3 buckets.

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Image resizing service (uksb-1tthgi812) (tag:s3-lambda-resizing-python)

Parameters:
  SourceBucketName:
    Type: String
    # Pass your bucket name dynamically or change it here
    Default: my-source-bucket-name
  DestinationBucketName:
    Type: String
    # Pass your bucket name dynamically or change it here
    Default: my-destination-bucket-name

Resources:
  ## S3 bucket
  SourceBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref SourceBucketName    
  DestinationBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref DestinationBucketName   

  ## Lambda function
  ResizerFunction:
    Type: AWS::Serverless::Function 
    Properties:
      CodeUri: src/
      Handler: app.lambda_handler
      Runtime: python3.12
      MemorySize: 2048
      Layers:
        - !Sub 'arn:aws:lambda:${AWS::Region}:175033217214:layer:graphicsmagick:2'
      Policies:
        - S3ReadPolicy:
            BucketName: !Ref SourceBucketName
        - S3CrudPolicy:
            BucketName: !Ref DestinationBucketName
      Environment:
        Variables:
          DESTINATION_BUCKETNAME: !Ref DestinationBucketName              
      Events:
        FileUpload:
          Type: S3
          Properties:
            Bucket: !Ref SourceBucket
            Events: s3:ObjectCreated:*
            Filter: 
              S3Key:
                Rules:
                  - Name: suffix
                    Value: '.jpeg'     
Outputs:
  SourceBucketName:
    Value: !Ref SourceBucketName
    Description: S3 Bucket for object storage
  DestinationBucketName:
    Value: !Ref DestinationBucketName
    Description: S3 destination Bucket for object storage
  FunctionArn:
    Value: !Ref ResizerFunction
    Description: ResizerFunction function  Arn