Resizing image with nodeJs and AWS

amazon-web-services, image-resizing, node.js

Solution

Got it working. Main reason was an extra parameter needed to be passed in to the `gm(response.Body, srcKey)`.

Full code:

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


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

exports.handler = function(event, context) {
    // Read options from the event.
    console.log("Reading options from event:\n", util.inspect(event, {depth: 5}));
    var srcBucket = event.Records[0].s3.bucket.name;
    var srcKey = event.Records[0].s3.object.key;

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

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

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

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

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

    var len = _sizesArray.length;

    console.log(len);
    console.log(srcBucket);
    console.log(srcKey);

    // 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;
    }

    // Download the image from S3, transform, and upload to same S3 bucket but different folders.
    async.waterfall([
            function download(next) {
                // Download the image from S3 into a buffer.

                s3.getObject({
                        Bucket: srcBucket,
                        Key: srcKey
                    },
                    next);
            },

            function transform(response, next) {


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

                    // Transform the image buffer in memory.
                    gm(response.Body, srcKey)
                        .resize(_sizesArray[i].width)
                        .toBuffer(imageType, function(err, buffer) {
                            if (err) {
                                next(err);

                            } else {
                                next(null, response.ContentType, buffer);
                            }
                        });
                }
            },

            function upload(contentType, data, next) {

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

                    // Stream the transformed image to a different folder.
                    s3.putObject({
                            Bucket: srcBucket,
                            Key: "dst/" + _sizesArray[i].destinationPath + "/" + _sizesArray[i].dstnKey,
                            Body: data,
                            ContentType: contentType
                        },
                        next);
                }
            }

        ], function (err) {
            if (err) {
                console.error(
                    '---->Unable to resize ' + srcBucket + '/' + srcKey +
                    ' and upload to ' + srcBucket + '/dst' +
                    ' due to an error: ' + err
                );
            } else {
                console.log(
                    '---->Successfully resized ' + srcBucket +
                    ' and uploaded to' + srcBucket + "/dst"
                );
            }

            context.done();
        }
    );
};

Problem

I am attempting to get an image from a `AWS S3` bucket using nodejs, resizing it into 4 different sizes and then saving it back to the same bucket but into a folder which in turn contains 4 folders, each for the new sizes. When I run the function, I get the following error: ``` Unable to resize devimageresize/diavelBlack.jpg and upload to / due to an error: Error: Stream yields empty buffer ``` I am relatively new to nodejs and am not sure I am writing the code correctly. What is causing this error? This is my code: ``` // dependencies var async = require('async'); var AWS = require('aws-sdk'); var gm = require('gm'); var util = require('util'); // get reference to S3 client var s3 = new AWS.S3(); exports.handler = function(event, context) { // Read options from the event. console.log("Reading options from event:\n", util.inspect(event, {depth: 5})); var srcBucket = event.Records[0].s3.bucket.name; var srcKey = event.Records[0].s3.object.key; var dstBucket = event.Records[0].s3.dst; var _800px = { width: 800, dstKey: 800 + srcKey, dstBucket: dstBucket.large }; var _500px = { width: 500, dstKey: 500 + srcKey, dstBucket: dstBucket.medium }; var _200px = { width: 200, dstKey: 200 + srcKey, dstBucket: dstBucket.small }; var _45px = { width: 45, dstKey: 45 + srcKey, dstBucket: dstBucket.thumbnail }; var _sizesArray = [_800px, _500px, _200px, _45px]; var len = _sizesArray.length; // Sanity check: validate that source and destination are same buckets. if (srcBucket == dstBucket) { console.error("Destination bucket must match source bucket."); } // 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; } // Download the image from S3, transform, and upload to same S3 bucket but different folders. async.waterfall([ function download(next) { // Download the image from S3 into a buffer. s3.getObject({ Bucket: srcBucket, Key: srcKey }, next); }, function transform(response, next) { for (var i = 0; i<len; i++) { // Transform the image buffer in memory. gm(response.Body).resize(_sizesArray[i].width) .toBuffer(imageType, function(err, buffer) { if (err) { next(err); } else { next(null, response.ContentType, buffer); } }); } }, function upload(contentType, data, next) { for (var i = 0; i<len; i++) { // Stream the transformed image to a different S3 bucket. s3.putObject({ Bucket: _sizesArray[i].dstBucket, Key: _sizesArray[i].dstKey, Body: data, ContentType: contentType }, next); } } ], function (err) { if (err) { console.error( 'Unable to resize ' + srcBucket + '/' + srcKey + ' and upload to ' + dstBucket + '/' + ' due to an error: ' + err ); } else { console.log( 'Successfully resized ' + srcBucket + '/' + srcKey + ' and uploaded to ' + dstBucket ); } context.done(); } ); }; ```

Original source