https://www.npmjs.com/package/captchapng
var http = require('http');
var captchapng = require('captchapng');
http.createServer(function (request, response) {
if(request.url == '/captcha.png') {
var p = new captchapng(80,30,parseInt(Math.random()*9000+1000)); // width,height,numeric captcha
p.color(0, 0, 0, 0); // First color: background (red, green, blue, alpha)
p.color(80, 80, 80, 255); // Second color: paint (red, green, blue, alpha)
var img = p.getBase64();
var imgbase64 = new Buffer(img,'base64');
response.writeHead(200, {
'Content-Type': 'image/png'
});
response.end(imgbase64);
} else response.end('');
}).listen(8181);