使用nodejs去做一个验证码

let express = require('express');
let captchapng = require('captchapng');
let app = express();


app.get('/cap',function (req, res) {

    res.render('html',{a,b,c,d})
        // width,height,   numeric captcha  数字验证码
    //他这个图片 每个数字之间是 80  这个图片的高度是30
    let num = parseInt(Math.random()*9000+1000);
    // cookie/session
    req.session.recode = num;
    let p = new captchapng(80,30,num);

    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)

    let img = p.getBase64();
    //将 base64图片格式 转成了 buffer
    let imgbase64 = new Buffer(img,'base64');

    res.set('Content-Type','image/png');
    res.send(imgbase64);
});


app.listen(3000,function () {
    console.log('start')
});