captcha-canvas API Documentation

A powerful and highly customizable CAPTCHA generator for Node.js applications, built on top of the fast skia-canvas rendering engine.

Quick Start

const { createCaptchaSync, CaptchaGenerator } = require("captcha-canvas");

// Simple generation
const { image, text } = createCaptchaSync(300, 100);

// Advanced generation with fluent API
const captcha = new CaptchaGenerator()
    .setDimension(150, 400)
    .setCaptcha({ characters: 6, size: 60 })
    .setTrace({ color: "#ff0000" });

const buffer = captcha.generateSync();
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Core Components

Classes

• CaptchaGenerator - High-level fluent interface for CAPTCHA generation
• Captcha - Low-level canvas manipulation and rendering

Functions

• createCaptcha - Async CAPTCHA generation with background support
• createCaptchaSync - Synchronous CAPTCHA generation (faster)
• resolveImage - Load and process background images

Interfaces & Types

• SetCaptchaOption - Configuration options for CAPTCHA text
• SetTraceOption - Configuration for trace lines
• SetDecoyOption - Configuration for decoy characters

Key Features

• Dual API Design: Simple functions for quick use, classes for advanced control
• Security Features: Trace lines, decoy characters, and visual distortions
• Customizable Styling: Fonts, colors, rotation, skewing, and opacity control
• Background Support: Custom background images (async generation only)
• Multi-styled Text: Array-based text configuration with different styles per segment
• TypeScript Ready: Full type definitions and IntelliSense support

Installation

# Install peer dependency first
npm install skia-canvas

# Install captcha-canvas
npm install captcha-canvas
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Links

• GitHub Repository - Source code and issues
• NPM Package - Package information and downloads
• Usage Examples - Comprehensive examples and patterns
• Technical Guide - Architecture and implementation details

For detailed usage examples, integration patterns, and troubleshooting, see the complete documentation sections below.