s3thumbnail.js

var im = require('imagemagick');
var aws = require('aws-sdk');
var s3 = new aws.S3({ apiVersion: '2006-03-01' });

exports.handler = function(event, context) {
    var bucket = event.Records[0].s3.bucket.name;
    var key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
    var params = {
        Bucket: bucket,
        Key: key
    };
    s3.getObject(params, function(err, data) {
        if (err) {
            console.log(err);
            var message = "Error getting object " + key + " from bucket " + bucket +
                ". Make sure they exist and your bucket is in the same region as this function.";
            console.log(message);
            context.fail(message);
        } else {
            var contentType = data.ContentType;
            var extension = contentType.split('/').pop();
            
            var filename = 'images/' + (key.match(/^origin\/(.+)$/) ? RegExp.$1 : key);

            im.resize({
                srcData: data.Body,
                format: extension,
                width: 480 // リサイズする画像サイズを指定
            }, function(err, stdout, stderr) {
                if(err) {
                    context.fail(err);
                    return;
                }
                s3.putObject({
                    Bucket: bucket,
                    Key : filename,
                    Body: new Buffer(stdout, 'binary'),
                    ACL : 'public-read',
                    ContentType: contentType
                }, function(err, res) {
                    if (err) {
                        context.fail(err);
                    } else {
                        context.succeed();
                    }
                });
            });
        }
    });
};