Serving thumbnails on-the-fly with Nettle and Express

server.js

var express = require('express');
var im = require('imagemagick');
var nettle = require('nettle');

var app = express.createServer();
var store = nettle.store({ url: 'mongodb://localhost:27017/mydb' });

// Create Nettle processor to resize image
var createProcessor = function(width) {
    store.processor(width, function(buffer, callback) {
        var params = {
            srcData: buffer.toString('binary'),
            width: parseInt(width, 10)
        };
        
        im.resize(params, function(err, stdout, stderr) {
            if (err) return callback(err);
            if (stderr) return callback(new Error(stderr));
            callback(null, new Buffer(stdout, 'binary'));
        });
    });
};

// Serve thumbnail
app.get('/images/:image/thumbnails/:width', function(req, res, next) {
    createProcessor(req.params.width);
    
    store.get(req.params.image, req.params.width, function(err, buffer) {
        if (err) return next(err);
        res.end(buffer, 'binary');
    });
});

app.listen(3000);