Skipper resize image before uploading using adapter

Question

I have a similar question to this one. How can I have this upload to my RackSpace adapter as well?

Here's the code:

upload: function(req, res){
        var RackspaceAdapter = require('../adapters/rackspace/index'),
            receiver = RackspaceAdapter.receive({
                username: sails.config.rackspace.username,
                apiKey: sails.config.rackspace.apiKey,
                region: sails.config.rackspace.region,
                container: sails.config.rackspace.container
            });
        req.file('file').upload(function (err, uploadedFiles) {
          if (err) return res.send(500, err);
            for(u in uploadedFiles){
                gm(uploadedFiles[u]).resize('500','','^').gravity('Center').crop('500','500').stream().pipe(receiver);
            }
          return res.json({
            message: uploadedFiles.length + ' file(s) uploaded successfully!',
            files: uploadedFiles
          });
        });
    },