sails.js - Skipper resize image before uploading using adapter -

i have similar question this one. how can have upload rackspace adapter well?

here's 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           });         });     },