How i can pipe image file to upload endpoint with superagent?

/**
 *  Request png
 */
 var request = require('superagent')
 var req = request.get('http://example.com/original/' + id + '.png');

 req.end(function(response){
   // Here i want send responsed image to another server
   req.post('http://upload-example.com').attach('???')
 })

How i can pipe image file to upload endpoint? I use latest version of superagent in nodejs env.