Node.JS - Encoding images in base64 using Buffer

Question

I'm trying to encode an image using base64 in Node.JS to pass along to the PostageApp API as an attachment. I thought I had it working but it attaches a 1K file that isn't exactly what I was looking for.

Here's my code:

 var base64data;

 fs.readFile(attachment, function(err, data) {
   base64data = new Buffer(data).toString('base64');
 });

And here's the part of the API call I am making:

 attachments: {
   "attachment.txt" : {
     content_type: "application/octet-stream",
     content: base64data
   },
 }

I'm a bit lost, not being so great with Node, but I thought it would work. Any help would be appreciated!

@Jim Schubert, that advice is wrong AND bad. First, readFile reads the whole file, not chunks. Second, blocking code would block the entire server, stupid idea. — thejh
– thejh, Commented Aug 15, 2011 at 18:14

thejh · Accepted Answer · 2011-08-15 18:13:37Z

47

fs.readFile(attachment, function(err, data) {
   var base64data = new Buffer(data).toString('base64');
   [your API call here]
});

It takes some time until the results are there, so by the time you've got the data, the outer scopes execution is already over.

answered Aug 15, 2011 at 18:13

thejh

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7 Comments

JonLim Over a year ago

Unfortunately, I pass base64data into a payload, which is essentially a JSON hash, which I then POST to the API server. Would this be preferable to what I'm doing?

thejh Over a year ago

@JonLim, this is basically the only way to do it. You'll have to do all that stuff ("pass base64data into a payload, which is essentially a JSON hash, which I then POST to the API server") inside the callback.

JonLim Over a year ago

Ah. No other way around it? That sucks, cause the attachments parameter is optional, so if there are no attachments, it doesn't get included. Thanks though!

thejh Over a year ago

@JonLim, in that case, create a named function for your callback and fire it directly if there are no attachments.

JonLim Over a year ago

Awesome, thank you! Another quick question though: what if I had multiple files to attach?

|

ellipse-of-uncertainty · Accepted Answer · 2015-04-27 14:56:21Z

13

Just specify "base64" as the encoding. Per the docs:

If no encoding is specified, then the raw buffer is returned.

fs.readFile(attachment, {encoding: 'base64'}, function(err, base64data) {
   [your API call here]
});

answered Apr 27, 2015 at 14:56

ellipse-of-uncertainty

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2 Comments

Sam Over a year ago

Isn't encoding for readFile the encoding of the attachment and not what you want to encode to?

Kennyhyun Over a year ago

in the document, The encoding can be any one of those accepted by Buffer. though it is of createReadStream. I've tried what @hyphenthis said and it worked.

holydragon · Accepted Answer · 2023-03-14 09:24:37Z

0

As of March 2023, I found this solution to be useful because the accepted answer is now deprecated. Use new Buffer.from along with base64 parameter instead of new Buffer does the trick.

base64data = new Buffer.from(data, 'base64').toString('base64');

answered Mar 14, 2023 at 9:24

holydragon

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1 Comment

Eri Feb 13 at 12:50

new is not needed. Buffer.from already creates a new Buffer.

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