Piping stdout from one command into stdin for another, and then to a writable stream

With the code in app.js I am able to pipe the output from the raspistill command spawned in camera() in camerautil.js to a writable stream. But instead of the writable stream, I want to pipe the output into the convert command spawned in resize() and then pipe stdout from that command to a writable stream.

What I have tried:

var streamOut = fs.createWriteStream('./image.jpg');
camerautil.camera().pipe(camerautil.resize(streamOut, 1, 1));

It throws the following error:

events.js:85
      throw er; // Unhandled 'error' event
            ^
Error: Cannot pipe. Not readable.
    at WriteStream.Writable.pipe (_stream_writable.js:162:22)
    at Object.exports.resize (/home/pi/dev/app/camerautil.js:27:14)
    at Object.<anonymous> (/home/pi/dev/app/index3.js:5:37)
    at Module._compile (module.js:460:26)
    at Object.Module._extensions..js (module.js:478:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Function.Module.runMain (module.js:501:10)
    at startup (node.js:129:16)
    at node.js:814:3

This is my (working) code:

app.js

var camerautil = require('./camerautil'),
    fs = require('fs');

var streamOut = fs.createWriteStream('./image.jpg');
camerautil.camera().pipe(streamOut);

camerautil.js

var spawn = require('child_process').spawn,
    Stream = require('stream');

exports.camera = function() {
    var child = spawn('raspistill', ['-w', 320, '-h', 240, '-n', '-t', 1, '-o', '-']);

    var stream = new Stream();

    child.stderr.on('data', stream.emit.bind(stream, 'error'));
    child.stdout.on('data', stream.emit.bind(stream, 'data'));
    child.stdout.on('end', stream.emit.bind(stream, 'end'));
    child.on('error', stream.emit.bind(stream, 'error'));

    return stream;
}

exports.resize = function(streamIn, width, height) {
    var child = spawn('convert', ['-', '-resize', width + 'x' + height, '-']);

    var stream = new Stream();

    child.stderr.on('data', stream.emit.bind(stream, 'error'));
    child.stdout.on('data', stream.emit.bind(stream, 'data'));
    child.stdout.on('end', stream.emit.bind(stream, 'end'));
    child.on('error', stream.emit.bind(stream, 'error'));

    streamIn.pipe(child.stdin);

    return stream;
}

I should mention that I'm running node v0.12.0 on a Raspberry Pi. The raspistill command is for taking pictures with the camera module. The convert command is part of ImageMagick.