fs.readFileSync('test.png', { encoding: 'base64' })

var gd = require('node-gd');
var img = gd.openPng('test.png');
var buff = Buffer.from(img.pngPtr(), 'binary');
var b64 = buff.toString('base64');

console.log(b64);

/home/ubuntu/workspace/test.js:16
var buff = Buffer.from(img.pngPtr(), 'binary');
                  ^

TypeError: binary is not a function
    at Function.from (native)
    at Function.from (native)
    at Object.<anonymous> (/home/ubuntu/workspace/test.js:16:19)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:139:18)
    at node.js:968:3

new Buffer(pngFile.pngPtr(), 'binary')