title: Node.js Stream picture via Filestream to gm
body: <p>i have a node server and will stream png-Files. The images are encrypted.
  With createReadStream i'm able to decrypt the file. Then i will resize the picture with gm (with graphicsmagick) but i do not know how to stream to gm and afterwards back to the client.</p>
  
  <p>All examples i found in web use gm with file input (i need a stream).</p>
  
  <p>Thanks a lot in advance.</p>
  
  <pre><code>var gm = require("gm");
  var rstream = fs.createReadStream(lPathPicture);  
  pRes.writeHead(200, {"Content-Type": "image/png"});  
  
  rstream  
      .pipe(aes)  // decrypt file  
     **.pipe(....)   // How to call gm with stream ?**  
      .pipe(pRes)  
      .on('finish', function () {  // finished  
          pRes.end();  
          return;  
      })  
      .on('error', function (err) {  // error  
          .....  
      });  
  </code></pre>