server.js

var im = require('imagemagick');
var Guid = require('guid');
var siteConf = require('./lib/getConfig');
var lib = new require('./lib/asms-client.js')(app, cf).streamLib;

function ingestPhoto(req, res, next){
  if (req.files.image) {
    im.identify(req.files.image.path, function(err, features){
      if (features && features.width) {
        var guid = Guid.create();
        // Concatenating name to guid guarantees that we always have
        // unique file names
        var fileId = guid + '/' + req.files.image.name;
        // The GridStore class is the equivalent of a File class but has the
        // added benefit of allowing you to store metadata
        var gs = lib.GridStore(lib.realMongoDB, fileId, "w", {
          content_type : req.files.image.type,
          // metadata is optional
          metadata : {
            author: req.session.user._id,
            public : false,
            filename: req.files.image.name,
            path: req.files.image.path,
            width: features.width,
            height: features.height,
            format: features.format,
            size_kb: req.files.image.size / 1024 | 0
          }
        });
         // This command copies the file from the file system(temp dir)
         // to GridFS.
         // GridFS supports any file size by breaking it into chunks
         // behind the scenes
        gs.writeFile(req.files.image.path, function(err, doc){
          if (err) {
            next(err);
          } else {
            if (! req.photosUploaded) {
              req.photosUploaded = {};
            }
            // I have another express route to serve the photos by fileId
            var url = siteConf.uri + "/photos/" + fileId;
            // Add the results of the upload to the chain
            req.photosUploaded['original'] = {url : url, metadata: gs.metadata};
            req.nextSizeIndex = 0;
            next();
          }
        });
      } else {
        if (err) throw err;
        throw(new Error("Cannot get width for photo"));
      }
    });
  } else {
    next(new Error("Could not find the file"));
  }
};