captcha.js

const Canvas = require('canvas')
const fs = require('fs')
let randomText = (length) => {
    let str = ''
    var range = 'abcdefghijklmnopqrstuvwxyz0123456789'
    for (i = 0; i < length; i++) {
        str += range.charAt(Math.floor(Math.random() * range.length))
    }
    return str
}
class Captcha {
    constructor(length) {
        if (isNaN(length) || !length) {
            var currentText = randomText(5)
        } else if (length < 5 || length > 10) {
            console.log(`captcha: Given length '${length}' was too long. Defaulted to 10 (Min: 5 Max: 10)`)
            var currentText = randomText(10)
        } else {
            var currentText = randomText(length)
        }
        this.length = length
        this.currentString = currentText
    }
    async image(string) {
        Canvas.registerFont('./assets/fonts/captcha-font.ttf', { family: 'captcha' })
        const canvas = Canvas.createCanvas(500, 200)
        const ctx = canvas.getContext('2d')
        const patterns = fs.readdirSync('./assets/patterns/')
        ctx.font = '50px captcha'
        let colors = ['#4e4ea3', '#22227d', '#0000cc', '#8e00fa']
        let minH = 50
        let maxH = canvas.height - minH
        ctx.fillStyle = colors[Math.floor(Math.random() * colors.length)]
        ctx.fillText(string, canvas.height / 2, Math.floor(Math.random() * maxH) + minH)
        ctx.globalAlpha = 0.3
        const pattern = await Canvas.loadImage('./assets/patterns/' + patterns[Math.floor(Math.random() * patterns.length)])
        ctx.drawImage(pattern, 0, 0, canvas.width, canvas.height)

        return canvas.toBuffer('image/png')
    }
}
module.exports.Captcha = Captcha