Nodejs image resizer with graphicmagick - node.js

Question

I have the following nodejs code, which as is it is, gets an image from AWS, resizes it into 4 different sizes and then saves it back into the AWS bucket into separate folders. However I need to write it so that it can be run on the dev environment as well. How could I write this so that depending on the input (local file on a vagrant machine, or on the AWS server) different functions are called (what to listen to?). It is worth noting that I am using AWS's new service Lambda.
// 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();
}
);
};

Answer 1

I would go for creating two providers(modules) i.e fsProvider and awsProvider with download, transform and upload methods. Then in handler i will decide which provider to use depending on process.end.NODE_ENV (development or production).