algebraic-captcha

Generate CAPTCHA from algebraic equation

DEMO

Install

Install package as yet another npm package:

npm install algebraic-captcha

Also yarn package manager can be used:

yarn add algebraic-captcha

Usage

Simple example.

const {AlgebraicCaptcha} = require('algebraic-captcha');
 
async function generateCaptcha() {
    const algebraicCaptcha = new AlgebraicCaptcha({
        width: 200,
        height: 200,
        background: '#ffffff',
        noise: 1,
        minValue: 1,
        maxValue: 10,
        operandAmount: 1,
        operandTypes: ['+', '-'],
        mode: 'formula',
        targetSymbol: '?'
    });
 
    const {image, answer} = await algebraicCaptcha.generateCaptcha();
}

Here:

• answer - is numeric answer for given equation (10 for this case).
• image - svg image string

Using inside express middleware.

const express = require('express');
const session = require('express-session');
const {AlgebraicCaptcha} = require('algebraic-captcha');
 
const app = express();
const algebraicCaptcha = new AlgebraicCaptcha({});
 
app.use(session({secret: 'my awesome session', resave: true}));
 
app.get('/captcha', async (req, res) => {
    const {image, answer} = await algebraicCaptcha.generateCaptcha();
    req.session.captcha = answer;
    res.writeHead(200, {'Content-Type': 'image/svg+xml'});
    res.end(image);
});
 
app.listen(3000);

Options

Available options:

width.

Width of generated image in pixels

• minimal value: 20
• minimal value: 1000
• default value: 200

height

Height of generated image in pixels

• minimal value: 20
• minimal value: 1000
• default value: 100

minValue

Min operand value used in equation

• minimal value: 1
• minimal value: 10000
• default value: 1

maxValue

Max operand value used in equation

• minimal value: 1
• minimal value: 10000
• default value: 1

background

Background color of captcha image

• default value: '#ffffff'

noise

Number of noise lines

• default value: 1

operandAmount

Number of equation operations

• default value: 1

operandTypes

Array of used math operators

• default value: ['+', '-']

mode

Can have two available values: formula, equation

In formula mode anwer placeholder will be put to the last position of generated string, such as:

5 + 2 = ?

In equation mode answer placeholder will be put on random operand position except last:

5 + ? = 7 //(or ? + 2 = 7)

• default value: 'formula'

targetSymbol

Symbol which is used as placeholder for answer

• default value: '?'

Development

Clone repository or its fork to local filesystem

git clone https://github.com/tormozz48/algebraic-captcha.git

Install npm dependencies:

npm install

Here are some suitable commands that can be used during development:

• npm run build - compile typescript files
• npm run lint - run tslint verification tool
• npm test - run tests with mocha
• npm run watch - launch watcher for compile source files during development

Important Use command npm run cm for commit your changes instead of git commit.

License

Apache-2.0

Support

Bugs, PRs, comments, suggestions welcomed!

Maintainer: Andrey Kuznetsov