📦 captcha-canvas-js

> A lightweight, framework-independent image captcha generator for Node.js — supports base64 output, in-memory or custom storage, and easy integration with Express, NestJS, Koa, etc.

!npm
!license

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✨ Features

- ✅ Generate random text-based image captchas (PNG)
- ✅ Supports Base64 image output
- ✅ Pluggable storage (in-memory, Redis, etc.)
- ✅ Fully written in TypeScript
- ✅ Framework-agnostic: works with Express, NestJS, Koa, etc.
- ✅ Includes CAPTCHA verification method

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📦 Installation

``bash
npm install
`

or

`bash
pnpm add captcha-canvas-js
`

---

🧱 Usage Example (Basic)

`ts
import { Captcha, MemoryStore } from "captcha-canvas-js";

const captcha = new Captcha(new MemoryStore());

const { id, imageBase64, text } = await captcha.generate();

console.log("Captcha ID:", id);
console.log("Captcha Text:", text); // You may skip logging this in production
console.log("Image (base64):", imageBase64);

// Later verify:
const isValid = await captcha.verify(id, "user-input");
`

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🧩 API

$3

- store: storage object (e.g., MemoryStore, or your own)
- options: optional customization:

`ts
{
width?: number; // default: 120
height?: number; // default: 40
length?: number; // number of characters (default: 4)
fontSize?: number; // default: 28
charset?: string; // default: A-Z + 2-9 (excluding O, I, 1)
background?: string; // e.g., "#f7f7f7"
noise?: number; // number of random lines (default: 3)
}
`

$3

Returns:

`ts
{
id: string;
text: string;
imageBase64: string; // starts with "data:image/png;base64,..."
}
`

$3

Checks if the user input matches the stored captcha text.

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🗃 Storage

$3

In-memory temporary store (auto-expire in 3 minutes by default).

$3

You can implement your own CaptchaStore (e.g., Redis):

`ts
export interface CaptchaStore {
set(id: string, value: string): Promise;
get(id: string): Promise;
delete(id: string): Promise;
}
`

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🔒 Security Notes

- Avoid exposing text in production
- Always expire stored captchas (e.g., 3–5 minutes)
- Rate limit captcha generation per IP/user if needed

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🧪 Development

`bash

build for ESM and CommonJS

npm run build
``

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📄 License

MIT

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notice

- The published package may have errors
- We will continue to update

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❤️ Author

Created by alias-- yiqishuyuan