Image Processing with S3, Lambda and CloudFront

import io
from urllib.parse import unquote_plus

import boto3
from PIL import Image, ImageOps

s3 = boto3.client("s3")
DEST_BUCKET = "bookshelf-thumbs-111122223333"
WIDTHS = (320, 640, 1280)
FORMATS = {"webp": ("WEBP", {"quality": 78, "method": 5}), "jpg": ("JPEG", {"quality": 80, "optimize": True})}


def handler(event, context):
    for record in event["Records"]:
        bucket = record["s3"]["bucket"]["name"]
        key = unquote_plus(record["s3"]["object"]["key"])               # for example covers/b81f/original.jpg
        prefix = key.rsplit("/", 1)[0]

        body = s3.get_object(Bucket=bucket, Key=key)["Body"].read()
        with Image.open(io.BytesIO(body)) as image:
            image = ImageOps.exif_transpose(image).convert("RGB")      # orientation, then sRGB, no metadata
            for width in WIDTHS:
                target = min(width, image.width)                         # never upscale
                resized = image.resize((target, round(image.height * target / image.width)), Image.Resampling.LANCZOS)
                for ext, (fmt, options) in FORMATS.items():
                    out = io.BytesIO()
                    resized.save(out, fmt, **options)
                    s3.put_object(
                        Bucket=DEST_BUCKET, Key=f"{prefix}/w{width}.{ext}", Body=out.getvalue(),
                        ContentType=f"image/{'webp' if ext == 'webp' else 'jpeg'}",
                        CacheControl="public, max-age=31536000, immutable",
                    )

npm install --cpu=x64 --os=linux sharp

import { S3Client, GetObjectCommand, PutObjectCommand } from '@aws-sdk/client-s3';
import sharp from 'sharp';

const s3 = new S3Client({});
const DEST_BUCKET = 'bookshelf-thumbs-111122223333';

export const handler = async (event) => {
  for (const record of event.Records) {
    const bucket = record.s3.bucket.name;
    const key = decodeURIComponent(record.s3.object.key.replace(/\+/g, ' '));
    const prefix = key.slice(0, key.lastIndexOf('/'));

    const { Body } = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
    const original = Buffer.from(await Body.transformToByteArray());

    for (const width of [320, 640, 1280]) {
      const base = sharp(original).rotate().resize({ width, withoutEnlargement: true });
      const variants = { webp: await base.clone().webp({ quality: 78 }).toBuffer(),
                         jpg: await base.clone().jpeg({ quality: 80, mozjpeg: true }).toBuffer() };
      for (const [ext, data] of Object.entries(variants)) {
        await s3.send(new PutObjectCommand({
          Bucket: DEST_BUCKET, Key: `${prefix}/w${width}.${ext}`, Body: data,
          ContentType: ext === 'webp' ? 'image/webp' : 'image/jpeg',
          CacheControl: 'public, max-age=31536000, immutable',
        }));
      }
    }
  }
};