Node.js convert an image to Base 64

gistfile1.js

//http://www.hacksparrow.com/base64-encoding-decoding-in-node-js.html
var fs = require('fs');

// function to encode file data to base64 encoded string
function base64_encode(file) {
    // read binary data
    var bitmap = fs.readFileSync(file);
    // convert binary data to base64 encoded string
    return new Buffer(bitmap).toString('base64');
}

// function to create file from base64 encoded string
function base64_decode(base64str, file) {
    // create buffer object from base64 encoded string, it is important to tell the constructor that the string is base64 encoded
    var bitmap = new Buffer(base64str, 'base64');
    // write buffer to file
    fs.writeFileSync(file, bitmap);
    console.log('******** File created from base64 encoded string ********');
}

// convert image to base64 encoded string
var base64str = base64_encode('salvarDocumento.png');
console.log(base64str);
// convert base64 string back to image 
base64_decode(base64str, 'copy_salvarDocumento.png');

Why the need to reallocate another buffer?

// function to encode file data to base64 encoded string
function base64_encode(file) {
  // read binary data
  const bitmap = fs.readFileSync(file);
  // convert binary data to base64 encoded string
  return bitmap.toString('base64');
}

No need to use two steps when you can use just one:
function base64_encode(file) {
const bitmap = fs.readFileSync(file, { encoding: 'base64' });
}

If you have only one option, you can directly specify it

function base64_encode(file) {
    const base64 = fs.readFileSync(file, 'base64');
}