image-captcha

NodeJS captcha image generator. This is a very basic captcha generator. It would be best used on an onion site or related. For clearnet sites, or other more proffesional applications, please look into Cloudflare's hCaptcha.
The default image size is 400x200px.

Installing

Install the npm package

npm install @likogan/image-captcha

Include the package in your code

const Captcha = require('@likogan/image-captcha');

Basic Use

Generate a Captcha

To generate a captcha

let newCaptcha = Captcha.genCaptcha();

Turn Captcha to Image

To turn the generated captcha into a PNG image in the applications root directory.

let newCaptcha = Captcha.genCaptcha();
Captcha.genImage(newCaptcha, 'image.png');

To generate the image in the directory src/captchas/captcha.png

Captcha.genImage(newCaptcha, 'src/captchas/captcha.png');

Verify Inputted Captcha

To verify if a captcha inputted by a user is valid, we can use the function verifyCaptcha()

let newCaptcha = Captcha.genCaptcha();

// This is two of the variables generated from "genCaptcha()"
let captchaToVerify = {
	id: 1677132092166,
  	hash: '$2b$04$tPz8CDNmrip.PSv69RFrvOTbVN072SSUqg9cRrleEsao3KoFXI0hW'
};
let userInput = 'IVPUVK';

if (Captcha.verifyCaptcha(captchaToVerify, userInput)) { // "verifyCaptcha()" returns boolean value
	console.log('Correct input');
} else {
	console.log('Invalid Input');
};

Further Documentation

genCaptcha()

Inputs

genCaptcha() allows for a json object input to change how it generates the image.

let config = {
	// ## Base Image
	width = 400, // Width of image
	height = 200, // Height of image
	bgColour: "#" + Math.floor(Math.random()*16777215).toString(16), // Background colour. Default is just random
	textColour: null // DO NOT LEAVE AS NULL! The text colour, unless otherwise specific, will be white or black depending on the bgColour. Controls the colour of shapes, lines, and random text seen in image.
	textColourReal: null // DO NOT LEAVE AS NULL! The real text colour, unless otherwise specific, will be the same as textColour. Only controls the colour of the real captcha text in the image.
	// ## Obfuscation
	lineWidth = 3, // Width of randomly genreated lines
	lines: Math.random()*20, // Amount of randomly generated lines
	shapes: Math.random()*20, // Amount of randomly generated shapes
	.shapesSizeMultiplier: 40, // Size multiplier of squares (still random!)
	// ## Text size, length, and rotation
	fontsize: 60, // Size of all text on image
	charLength: 6, // Length of real captcha
	rotatemax: 30, // Maximum (right) rotation - too high makes it very hard to read
	rotatemin: -30, // Minimum (left) rotation - too high makes it very hard to read
	// # Authentication
	hashSalt: 2 // The rounds of the hashed value of the captcha
}

let newCaptcha = Captcha.genCaptcha(config);

Outputs

{
  png: <Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 01 90 00 00 00 c8 08 06 00 00 00 c6 15 b7 e2 00 00 00 06 62 4b 47 44 00 ff 00 ff 00 ff a0 bd a7 ... 22344 more bytes>,
  text: 'IVPUVK',
  id: 1677132092166,
  hash: '$2b$04$tPz8CDNmrip.PSv69RFrvOTbVN072SSUqg9cRrleEsao3KoFXI0hW'
}

png The raw data of the generated PNG image. This value can be used alongside genImage() to generate the full Captcha image. text The real text of the captcha. Do not send this to the user! id A generated ID used in the hash. It's just the current date in milliseconds. Used in verifyCaptcha(). Can also be used for your own custom verification method. hash The hash of text and id. Used for verifyCaptcha()

genCaptchav2()

Identical to genCaptcha(), but uses the following custom config

let bgColour = "#000000".replace(/0/g,function(){return (~~(Math.random()*16)).toString(16)});
const config = {
	// ## Image
	width: 400,
	height: 200,
	bgColour: bgColour,
	realTextColour: bgColour,
	// ## Obfuscation
	lineWidth: 2,
	lines: 100,
	shapes: genRandom(10, 40),
	shapesSizeMultiplier: 40,
}

genImage()

Generates an image using the returned png variable from genCaptcha().

Inputs

genImage() requires two inputs. The captcha data, and the location of the image.

Captcha Data

Uses png from genCaptcha() to generate a PNG image.

{
  png: <Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 01 90 00 00 00 c8 08 06 00 00 00 c6 15 b7 e2 00 00 00 06 62 4b 47 44 00 ff 00 ff 00 ff a0 bd a7 ... 22344 more bytes>, ..

Input the whole object from genCaptcha()

let newCaptcha = Captcha.genCaptcha()

Captcha.genImage(newCaptcha, 'image.png')

Image Location

The second input is the image path in a string. Examples: image.png src/captchas/captcha.png

You can even get creative and use other variables to define a better suited path. For example, let's name the captcha image the date/time it was created, and under the web path of /var/www. The final path sould look like /var/www/website/images/captchas/1677132092166.png

let newCatpcha = genCaptcha()

let location = '`/var/www/website/images/captchas/${newCaptcha.id}.png`
Captcha.genImage(newCaptcha, location)

verifyCaptcha()

This function is very simple. It just comapares the user inputted captcha text, and the generated captcha object.

Inputs

verifyCaptcha() requires two inputs. One of the generated captcha object, and the other of the user inputted captcha text.

Captcha Object

{
  id: 1677132092166,
  hash: '$2b$04$tPz8CDNmrip.PSv69RFrvOTbVN072SSUqg9cRrleEsao3KoFXI0hW'
}

verifyCaptcha(newCaptcha, ..)

Guessed Captcha Text

The next is just the guessed captcha text from the user.

let newCaptcha = Captcha.genCaptcha();

// This is two of the variables generated from "genCaptcha()"
let captchaToVerify = {
	id: 1677132092166,
  	hash: '$2b$04$tPz8CDNmrip.PSv69RFrvOTbVN072SSUqg9cRrleEsao3KoFXI0hW'
};
let userInput = 'IVPUVK';

console.log(verifyCaptcha(captchaToVerify, userInput))

Ouputs

verifyCaptcha() returns a boolean, true or false, depending on if the captcha is correct or not.

if (Captcha.verifyCaptcha(captchaToVerify, userInput)) { // "verifyCaptcha()" returns boolean value
	console.log('Correct input');
} else {
	console.log('Invalid Input');
};

Acknowledgments

NodeJS modules

canvas (npm) (github) - Used for image generation.
invert-color (npm) (github) - Used to determine if the text on the generated captcha image should be black or white.
bcrypt (npm) (github) - Used for hashing generated captcha data, and for authenticating captchas

Fonts

OpenSans by Steve Matteson (google fonts)