Uploading base64 encoded Image to Amazon S3 via Node.js


Yesterday I did a deep night coding session and created a small node.js/JS (well actually CoffeeScript, but CoffeeScript is just JavaScript so lets say JS) app.

what's the goal:

  1. client sends a canvas datauri (png) to server (via socket.io)
  2. server uploads image to amazon s3

step 1 is done.

the server now has a string a la


my question is: what are my next steps to "stream"/upload this data to Amazon S3 and create an actual image there?

knox https://github.com/LearnBoost/knox seems like an awesome lib to PUT something to S3, but what I'm missing is the glue between the base64-encoded-image-string and actual upload action?

Any ideas, pointers and feedback welcome.

11/26/2017 10:48:06 AM

Accepted Answer

For people who are still struggling with this issue. Here is the approach I used with native aws-sdk.

var AWS = require('aws-sdk');
var s3Bucket = new AWS.S3( { params: {Bucket: 'myBucket'} } );

inside your router method :- ContentType should be set to the content type of the image file

  buf = new Buffer(req.body.imageBinary.replace(/^data:image\/\w+;base64,/, ""),'base64')
  var data = {
    Key: req.body.userId, 
    Body: buf,
    ContentEncoding: 'base64',
    ContentType: 'image/jpeg'
  s3Bucket.putObject(data, function(err, data){
      if (err) { 
        console.log('Error uploading data: ', data); 
      } else {
        console.log('succesfully uploaded the image!');

s3_config.json file is:-

9/30/2014 2:00:47 AM

ok, this one is the answer how to save canvas data to file

basically it loos like this in my code

buf = new Buffer(data.dataurl.replace(/^data:image\/\w+;base64,/, ""),'base64')

req = knoxClient.put('/images/'+filename, {
             'Content-Length': buf.length,

req.on('response', (res) ->
  if res.statusCode is 200
      console.log('saved to %s', req.url)
      socket.emit('upload success', imgurl: req.url)
      console.log('error %d', req.statusCode)


Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow