Node.js base64 encode a downloaded image for use in data URI

Question

Using Node v0.2.0 I am trying to fetch an image from a server, convert it into a base64 string and then embed it on the page in an image tag. I have the following code:

Answer 1

The problem is encoding and storing binary data in javascript strings. There's a pretty good section on this under Buffers at http://nodejs.org/api.html.

Unfortunately, the easiest way to fix this involved changing the request npm. I had to add response.setEncoding('binary'); on line 66 just below var buffer; in /path/to/lib/node/.npm/request/active/package/lib/main.js. This will work fine for this request but not others. You might want to hack it so that this is only set based on some other passed option.

I then changed var buf = new Buffer(body) to var buf = new Buffer(body, 'binary');. After this, everything worked fine.

Another way to do this, if you really didn't want to touch the request npm, would be to pass in an object that implements Writable Stream in the responseBodyStream argument to request. This object would then store the streamed data from the response in it's own buffer. Maybe there is a library that does this already... i'm not sure.

I'm going to leave it here for now, but feel free to comment if you want me to clarify anything.

EDIT

Check out comments. New solution at http://gist.github.com/583836

Answer 2

This works for me using request:

const url = 'http://host/image.png';
request.get({url : url, encoding: null}, (err, res, body) => {
    if (!err) {
        const type = res.headers["content-type"];
        const prefix = "data:" + type + ";base64,";
        const base64 = body.toString('base64');
        const dataUri = prefix + base64;
    }
});

No need for any intermediate buffers. The key is to set encoding to null.

Answer 3

The following code (available at https://gist.github.com/804225)

var URL = require('url'),
    sURL = 'http://nodejs.org/logo.png',
    oURL = URL.parse(sURL),
    http = require('http'),
    client = http.createClient(80, oURL.hostname),
    request = client.request('GET', oURL.pathname, {'host': oURL.hostname})
;

request.end();
request.on('response', function (response)
{
    var type = response.headers["content-type"],
        prefix = "data:" + type + ";base64,",
        body = "";

    response.setEncoding('binary');
    response.on('end', function () {
        var base64 = new Buffer(body, 'binary').toString('base64'),
            data = prefix + base64;
        console.log(data);
    });
    response.on('data', function (chunk) {
        if (response.statusCode == 200) body += chunk;
    });
});

should also produce a data URI without requiring any external modules.