Node resize image and upload to AWS

I'm relatively new to node, and want to write a module that takes an image from an S3 bucket, resizes it and saves it to a temporary directory on Amazon's new Lambda service and then uploads the images back to the bucket.

When I run the code, none of my functions seem to be called (download, transform and upload). I am using tmp to create the temporary directory and graphicsMagick to resize the image.

What is wrong with my code?

I have defined the dependencies and the array outside of the module, because I have another which depends on these.

// dependencies
var AWS = require('aws-sdk');
var gm = require('gm').subClass({ imageMagick: true });
var fs = require("fs");
var tmp = require("tmp");

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

var _800px = {
    width: 800,
    destinationPath: "large"
};

var _500px = {
    width: 500,
    destinationPath: "medium"
};

var _200px = {
    width: 200,
    destinationPath: "small"
};

var _45px = {
    width: 45,
    destinationPath: "thumbnail"
};

var _sizesArray = [_800px, _500px, _200px, _45px];

var len = _sizesArray.length;

exports.AwsHandler = function(event) {
    // Read options from the event.
    var srcBucket = event.Records[0].s3.bucket.name;
    var srcKey = event.Records[0].s3.object.key;
    var dstnKey = srcKey;

    // create temporary directory
    var tmpobj = tmp.dirSync();

    // function to determine paths
    function _filePath (directory, i) {
        if (!directory) {
            return "dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
        } else {
            return directory + "/dst/" + _sizesArray[i].destinationPath + "/" + dstnKey;
        }
    };


    // Infer the image type.
    var typeMatch = srcKey.match(/\.([^.]*)$/);
    if (!typeMatch) {
        console.error('unable to infer image type for key ' + srcKey);
        return;
    };

    var imageType = typeMatch[1];

    if (imageType != "jpg" && imageType != "png") {
        console.log('skipping non-image ' + srcKey);
        return;
    };


    (function resizeImage () {
        function download () {

            console.log("started!");

            s3.getObject({
                    Bucket: srcBucket,
                    Key: srcKey
                },
                function (err, response) {
                    if (err) {
                        console.error(err);
                    }
                    // call transform if successful
                    transform (response);
                }
            );
        };

        function transform (response) {

            for ( var i = 0; i<len; i++ ) {

                // define path for image write
                var _Key = _filePath (tmpobj, i);

                // resize images
                gm(response.Body, srcKey)
                    .resize(_sizesArray[i].width)
                    .write(_Key, function (err) {
                        if (err) {
                            console.error(err);
                        }
                        upLoad ();
                    });
            }
        };

        function upLoad () {

            for ( var i = 0; i<len; i++ ) {

                var readPath = _filePath (tmpobj, i);

                var writePath = _filePath (i);

                // read file from temp directory
                fs.readFile(readPath, function (err, data) {
                    if (err) {
                        console.error(err);
                    }

                    // upload images to s3 bucket
                    s3.putObject({
                        Bucket: srcBucket,
                        Key: writePath,
                        Body: data,
                        ContentType: data.type
                    },
                    function (err) {
                        if (err) {
                            console.error(err);
                        }
                        console.log("Uploaded with success!");
                    });
                })
            }
            // Manual cleanup of temporary directory
            tmpobj.removeCallback();
        };
    }());
};