Node.js and OpenCV

Question

I am having trouble getting face tracking and detection from the npm opencv package. I'm currently just trying to drawing a circle each face.

I have listed below the error and the files below that. I'm not sure if its just a binding issue, if so what steps should I take to resolve it.

OpenCV (2.4.8.2) was installed via brew FYI - It could be a versions thing I guess

Error:

/Users/gwilliams2/Sites/facetracking/node_modules/opencv/lib/opencv.js:29
      var face_cascade = new cv.CascadeClassifier(classifier);
                         ^
TypeError: Error loading file
    at Matrix.matrix.detectObject (/Users/gwilliams2/Sites/facetracking/node_modules/opencv/lib/opencv.js:29:23)
    at /Users/gwilliams2/Sites/facetracking/server.js:170:8
    at Socket.<anonymous> (/Users/gwilliams2/Sites/facetracking/server.js:161:11)
    at Socket.EventEmitter.emit [as $emit] (events.js:95:17)
    at SocketNamespace.handlePacket (/Users/gwilliams2/Sites/facetracking/node_modules/socket.io/lib/namespace.js:335:22)
    at Manager.onClientMessage (/Users/gwilliams2/Sites/facetracking/node_modules/socket.io/lib/manager.js:488:38)
    at WebSocket.Transport.onMessage (/Users/gwilliams2/Sites/facetracking/node_modules/socket.io/lib/transport.js:387:20)
    at Parser.<anonymous> (/Users/gwilliams2/Sites/facetracking/node_modules/socket.io/lib/transports/websocket/hybi-16.js:39:10)
    at Parser.EventEmitter.emit (events.js:95:17)
    at finish (/Users/gwilliams2/Sites/facetracking/node_modules/socket.io/lib/transports/websocket/hybi-16.js:288:16)

client.js

var APP = {

    // setup the web socket
    socket: io.connect('http://gaz.local:3000'),
    video: null,
    canvas: null,
    imgData: null,

    init: function (){

        // get elements
        APP.video = $('#myVideo')[0];
        APP.canvas = $('#myCanvas')[0];

        // start app
        APP.main();

    },

    main: function(){

      // if we can get a webcam
      if(APP.hasGetUserMedia()){

          navigator.webkitGetUserMedia(
                  {video:true, audio:false},
                  APP.videoSuccess,
                  APP.videoError
              );

      } else {

          alert('Sorry, you do not have webcam access');
      }

    },

    hasGetUserMedia: function (){

      return !!(navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia);

    },

    videoSuccess: function (stream){

      // set the video to stream
      APP.video.src = window.URL.createObjectURL(stream);

      // set canvas size
      APP.canvas.width = APP.video.width;
      APP.canvas.height = APP.video.height;

      // draw video
      var i = 0;
      setTimeout(function(){

        // darw the image to the canvas
        APP.canvas.getContext('2d').drawImage(APP.video, 0, 0);

        APP.imgData = APP.canvas.toDataURL('image/jpeg');
        APP.imgData = APP.imgData.replace('data:image/jpeg;base64,', '');

        // send the file in json format to the server
        var jsonData = JSON.stringify({imgData: APP.imgData, count: i});
        APP.socket.emit('update', jsonData);

        // APP.socket.on('put_down', function (data) {
        //   console.log(data);
        // });


        // update the counter
        i++;

      }, 50);

    },

    videoError: function (err){
      alert('Error: ' + err);
    },

};

$(function (){ APP.init(); });

Server.js

/*
    Setup a server, RTC and face tracking

    Install opencv
        brew install opencv
    NPM
        https://www.npmjs.org/package/fs
        https://www.npmjs.org/package/http
        https://www.npmjs.org/package/express
        https://www.npmjs.org/package/socket.io
        https://www.npmjs.org/package/opencv
*/
var APP = {

    // include some scripts
    server: null,
    port: 3000,
    express: require('express'),
    app: null,
    mdb: require('mongodb'),
    dbUrl: 'mongodb://127.0.0.1:27017/test',
    db: null,
    io: null,
    cv: require('opencv'),
    fs: require("fs"),

    init: function (){

        // connect stuff up
        APP.app = APP.express();
        APP.server = require('http').createServer(APP.app).listen(APP.port, '0.0.0.0');
        APP.io = require('socket.io').listen(APP.server);

        // http routing
        APP.routing();

        // connect the websocket
        APP.io.on('connection', function (socket){

            console.log('Server started on port ' + APP.port);
            APP.main(socket);

        });

    },

    // open the db
    openDB: function (){

        APP.mdb.connect(APP.dbURL, function(err, db){

            if(err)
                throw err;

            APP.db = db;

        });

    },

    // close the db
    closeDB: function (){

        APP.db.close();

    },

    // insert a file to the db
    dbInsert: function (col, data){

        // open the db
        APP.openDB();

        var collection = APP.db.collection(col);
        collection.insert(data, function(err, docs){
            if(err){
                console.warn(err.message);
            } else {
                console.log('Successfully inserted record');
            }
        });

        // close the db
        APP.closeDB();

    },

    // insert a file to the db
    dbUpdate: function (col, crit, data){

        // open the db
        APP.openDB();

        var collection = APP.db.collection(col);
        collection.update(crit, {$set: {hi: 'there'}}, {w:1}, function (){
            if(err){
                console.warn(err.message);
            } else {
                console.log('Successfully updated record');
            }
        });

        // close the db
        APP.closeDB();

    },

    // find a file in the db
    dbFind: function (col){

        // open the db
        APP.openDB();

        var collection = APP.db.collection(col);
        collection.find().toArray(function(err, results) {
            console.dir(results);
        });

        // close the db
        APP.closeDB();

    },

    // routing files
    routing: function (){

        // set directory to use for files prefixed with /library
        APP.app.use('/library', APP.express.static(__dirname + '/library'));

        // index page
        APP.app.get('/*', function (req, res){

            // get query
            // console.log(req.query);

            // get file
            res.sendfile(__dirname + '/' + req.route.params);

        });

    },

    main: function (socket){

        //  APP.io.sockets.emit('put_down', {'fingers': 's'});
        socket.on('update', function (data) {

            // console.log(data);

            // get the data
            data = JSON.parse(data);

            // create the file
            var filename = 'file' + data.count + '.jpg';
            APP.fs.writeFile(filename, data.imgData, 'base64', function(err) {
                if(err)
                    console.log(err);
            });

            // open file with open cv
            APP.cv.readImage(filename, function(err, im){

                // handle errors
                if(err)
                    return err;

                console.log(im);

                // /Users/gwilliams2/Sites/facetracking/node_modules/opencv/data/haarcascade_frontalface_default.xml
                im.detectObject('./haarcascade_frontalface_default.xml', {}, function(err, faces){
                    for (var i=0;i<faces.length; i++){
                        var x = faces[i];
                        im.ellipse(x.x + x.width/2, x.y + x.height/2, x.width/2, x.height/2);
                    }

                    im.save('./out.png');   
                });

            });

        });

    }

};

// run the script
APP.init();

Answer 1

Solved, firstly, I had linked to the xml file incorrectly, as the path was incorrect as suggested in the comments above. I then noticed the buffer for the open file had been close. Since everything is asynchronous, the code in the server for analysing the file needs to be nested in the file saving callback.