algebraic-captcha

Generate CAPTCHA from algebraic equation


DEMO

Install

Install package as yet another npm package:

``bash
npm install algebraic-captcha
`

Also yarn package manager can be used:

`bash
yarn add algebraic-captcha
`

Usage

Simple example.

`js
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
!image

Using inside express middleware.

`js
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

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

Install npm dependencies:

`bash
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