NodeJS code to resize images while keeping the original aspect ratio

resize_images.js

// Create clients outside of the handler


// Create a client to read objects from S3
const AWS = require('aws-sdk');
const s3 = new AWS.S3();


// Libraries for image resize.
const stream = require('stream');
const sharp = require('sharp');

// Function to create a read stream to an S3 object.
const readStreamFromS3 = ({Bucket, Key}) => {
    return s3.getObject({Bucket, Key}).createReadStream();
};

// Function to create a write stream to S3.
const writeStreamToS3 = ({Bucket, Key}) => {
    const pass = new stream.PassThrough();
    return {
        writeStream: pass,
        uploadFinished: s3.upload({
            Body: pass,
            Bucket,
            ContentType: 'image/jpeg',
            Key
        }).promise()
    };
};

// Get size from stream (sharp)
const getSizeFromStream = () => {
    const pass = new stream.PassThrough();
    const metadata = sharp(pass).metadata().then(metadata =>
        {
            return {
                writeStream: pass,
                width: metadata.width,
                height: metadata.height
            };

        });
};


// Resize image stream (sharp).
const resizeStream = ({width, height}) => {
    return sharp()
        .resize(width, height)
        .toFormat('jpeg');
};

/**
  * A Lambda function that logs the payload received from S3.
  */
exports.resizeImagesHandler = async (event, context) => {
    const getObjectRequests = event.Records.map(async (record) => {
        const params = {
            Bucket: record.s3.bucket.name,
            Key: record.s3.object.key,
        };

        try {
            // First, copy the original to a new file.
            const fileExt = record.s3.object.key.split('.').pop();
            const splitKey = record.s3.object.key.split('/');
            const prefix = splitKey.splice(-1, 0, "orig");
            const newKey = splitKey.join('/');

            // Show keys and stuff.
            console.log('File extension: ' + fileExt);
            console.log('Split key:' + splitKey);
            //console.log('prefix:' + prefix);
            console.log('newKey: ' + newKey);
            const readStreamOrig = readStreamFromS3(params);

            // Create a pipeline inline to read the metadata.
            //let origWidth;
            //let origHeight;
            //const pipeline = sharp().metadata().then(metadata =>{
            //    origWidth = metadata.width;
            //    origHeight = metadata.height;
            //});

            const {
                passThroughStream,
                origWidth,
                origHeight
            } = getSizeFromStream();

            const {
                writeStreamOrig,
                uploadFinishedOrig
            } = writeStreamToS3({Bucket: params[0], Key: newKey});

            readStreamOrig
                .pipe(passThroughStream)
                .pipe(writeStreamOrig);

            const uploadedData = await uploadFinishedOrig;

            console.log("Original width: " + origWidth);
            console.log("Original height: " + origHeight);

            console.log('Image was reuploaded', {
                ...uploadedData
            });

            // Have to determine the original width and height.
            // Can that be done through a stream, or does it have to be done
            // before processing?
            // Compute ratio of width/height. width will always be 500 pixels in the end.
            const ratio = origWidth / origHeight;
            const readStream = readStreamFromS3({Bucket: params[0], Key: newKey});
            const resizeStreamVar = resizeStream({width: 500, height: 500/ratio});
            const {
                writeStream,
                uploadFinished
            } = writeStreamToS3({Bucket: params[0], Key: params[1]});

            // Trigger the stream.
            readStream
                .pipe(resizeStreamVar)
                .pipe(writeStream);

            const uploadedDataResized = await uploadFinished;

            console.log('Image was resized:', {
                ...uploadedDataResized
            });

        } catch (error) {
            console.log('Error calling S3 getObject: ' + error);
            console.error('Error calling S3 getObject:' + error);
            throw error;
        }
    });

    await Promise.all(getObjectRequests);
};