sending binary data to pure nodejs

i am posting binary image data to nodejs and receiving it using the following code concept

var requestBody = '';
this.request.on('data', function (data) {
    requestBody += data;
    if (requestBody.length > 1e6 * config.POST_MAX_SIZE) {
        // FLOOD ATTACK OR FAULTY CLIENT, NUKE REQUEST
        this.request.connection.destroy();
    }
});
this.request.on('end', function () {
    this.post = qs.parse(requestBody);
});

because i concat the data as string i get the image data as a string representation in the form of:

<ffd8ffe0 00104a46 49460001 01000048 00480000 ffe10058 45786966 00004d4d 002a0000 00080002 01120003 00000001 00010000 87690004 00000001 ....

now how can i return this data to binary and save it to a file, i have tried this code, its save the image but the image is corrupted:

 fs.writeFile("myimage.jpg", new Buffer(this.post.imageData, 'binary') ,function(err){});

when i open the image in a text editor its still in the form

<ffd8ffe0 00104a46 49460001 01000048 00480000 ffe10058 45786966 00004d4d 002a0000 00080002 01120003 00000001 00010000 87690004 00000001 ....