Passing file in S3 to function Lambda

Here’s some example code showing get and put from S3 in Lambda

// dependencies
const AWS = require('aws-sdk');
const util = require('util');
const sharp = require('sharp');

// get reference to S3 client
const s3 = new AWS.S3();

exports.handler = async (event, context, callback) => {

// Read options from the event parameter.  
console.log("Reading options from event:\n", util.inspect(event, {depth: 5}));  
const srcBucket = event.Records\[0].s3.bucket.name;  
// Object key may have spaces or unicode non-ASCII characters.  
const srcKey    = decodeURIComponent(event.Records\[0].s3.object.key.replace(/\+/g, " "));  
const dstBucket = srcBucket + "-resized";  
const dstKey    = "resized-" + srcKey;  

// Infer the image type from the file suffix.  
const typeMatch = srcKey.match(/\.(\[^.]*)$/);  
if (!typeMatch) {  
    console.log("Could not determine the image type.");  
    return;  
}  

// Check that the image type is supported    
const imageType = typeMatch\[1].toLowerCase();  
if (imageType != "jpg" && imageType != "png") {  
    console.log(`Unsupported image type: ${imageType}`);  
    return;  
}  

// Download the image from the S3 source bucket.   

try {  
    const params = {  
        Bucket: srcBucket,  
        Key: srcKey  
    };  
    var origimage = await s3.getObject(params).promise();  

} catch (error) {  
    console.log(error);  
    return;  
}    

// set thumbnail width. Resize will set the height automatically to maintain aspect ratio.  
const width  = 200;  

// Use the Sharp module to resize the image and save in a buffer.  
try {   
    var buffer = await sharp(origimage.Body).resize(width).toBuffer();  
          
} catch (error) {  
    console.log(error);  
    return;  
}   

// Upload the thumbnail image to the destination bucket  
try {  
    const destparams = {  
        Bucket: dstBucket,  
        Key: dstKey,  
        Body: buffer,  
        ContentType: "image"  
    };  

    const putResult = await s3.putObject(destparams).promise();   
      
} catch (error) {  
    console.log(error);  
    return;  
}   
      
console.log('Successfully resized ' _ srcBucket _ '/' _ srcKey _  
    ' and uploaded to ' _ dstBucket _ '/' + dstKey);   

};