mongodb gridfs encoding picture base64 - node.js

Question

i try to readout an image, saved in mongodb, via gridfs (without temporary file)
it should be directly sent to ajax, which injects it into html
when i use my actual functions a large bit string is formed and sent to client (is saved in ajax response var)
but as it reaches the client, the bits arent correct anymore
so i look for a way to encode the picture before it is sent (into base64)
(or is there any other way?)
Serverside - javascript, gridfs
exports.readFileFromDB = function(req, res, profile, filename, callback){
console.log('Find data from Profile ' + JSON.stringify(profile));
var GridReader = new GridStore(db, filename,"r");
GridReader.open(function(err, gs) {
var streamFile = gs.stream(true);
streamFile.on("end", function(){
});
// Pipe out the data
streamFile.pipe(res);
GridReader.close(function(err, result) {
});
Clientside - javascript ajax call:
function imgUpload(){
var thumb = $("#previewPic");
$('#uploadForm').ajaxSubmit({
beforeSend:function(){
//launchpreloader();
},
error: function(xhr) {
//status('Error: ' + xhr.status);
},
success: function(response) {
console.log(response);
var imageData = $.base64Encode(response);
console.log(imageData);
thumb.attr("src","data:image/png;base64"+imageData);
$("#spanFileName").html("File Uploaded")
}
});
}

Answer 1

I'm doing something similar for a current project, but when the upload is complete, I return a JSON object containing the URL for the uploaded image:
{ success : true, url : '/uploads/GRIDFSID/filename.ext' }
I have a route in Express that handles the /uploads route to retrieve the file from GridFS and stream it back to the client, so I can use the above URL in an IMG SRC. This is effectively what appears in the DOM:
<img src="/uploads/GRIDFSID/filename.ext">
The route handler looks something like this (it uses node-mime and gridfs-stream):
app.get(/^\/uploads\/([a-f0-9]+)\/(.*)$/, function(req, res) {
var id = req.params[0];
var filename = req.params[1];
// Set correct content type.
res.set('Content-type', mime.lookup(filename));
// Find GridFS file by id and pipe it to the response stream.
gridfs
.createReadStream({ _id : id })
.on('error', function(err) {
res.send(404); // or 500
})
.pipe(res);
});
It obviously depends on your exact setup if my solution works for you.