Meteor image file upload. Then send file to S3.

client_example.html

Template.example.events({
  'change input': function(ev) {  
    _.each(ev.srcElement.files, function(file) {
      Meteor.saveFile(file, file.name);
    });
  }
});

client_example.js

<template name="example">
<input type=file />
</template>

client_save_file.js

// original source from file upload gist
// https://gist.github.com/dariocravero/3922137

Meteor.saveFile = function(blob, name, path, type, callback) {
  var fileReader = new FileReader(),
    method, encoding = 'binary', type = type || 'binary';
  switch (blob.type) {
    case 'image/png': 
    case 'image/jpeg': 
      method = 'readAsBinaryString';
      encoding = 'binary';
      
      fileReader.onload = function(file) {
        Meteor.call('saveFile', file.srcElement.result, Session.get("documentId"), path,
                    encoding, blob.type, callback);
      }
      
      break;
    default:
      method = 'readAsBinaryString';
      encoding = 'binary';
      break;
  }
  
  fileReader[method](blob);
}

server_save_file.js

function getS3Bucket() {
  if (Meteor.absoluteUrl() === 'http://localhost:3000/') {
    return 'myapp-dev';
  } else if (Meteor.absoluteUrl() === 'http://myapp.meteor.com/') {
    return 'myapp-staging';
  } else if (Meteor.absoluteUrl() === 'http://myapp.com/') {
    return 'myapp-production';
  }
}

Meteor.methods({
  saveFile: function(blob, name, path, encoding, type) {
    var knox = Meteor.require('knox');
    var client = knox.createClient({
      key: '' /* S3 Key */,
      secret: '' /* S3 Secret */,
      bucket: getS3Bucket()
    });
    
    // from meteor async gist
    // https://gist.github.com/possibilities/3443021
    Future = Meteor.require('fibers/future');
    var fut = new Future();
    var buffer = new Buffer(blob, 'binary');
    client.putBuffer(buffer, '/thumbnails/' + name, {
      'Content-Length':blob.length,
      'Content-Type':type,
      'x-amz-acl': 'public-read'
    }, function(err, res) {
      fut.return(name);
    });
    fut.wait();
  },
  removeThumb: function (name) {
    var knox = Meteor.require('knox');
    var client = knox.createClient({
      key: '' /* S3 Key */,
      secret: '' /* S3 Secret */,
      bucket: getS3Bucket()
    });
    client.deleteFile('/thumbnails/' + name, function(err, res) {
    });
  }
});