FreezeLib is a Go library for generating beautiful screenshots of code and terminal output. It's based on the popular freeze CLI tool by Charm, but redesigned as a reusable library for Go applications.

Features

🎨 Syntax Highlighting: Support for 270+ programming languages
🔍 Auto Language Detection: Intelligent language detection from code content and filenames
📋 Simple Lists: Easy access to all available languages, themes, and presets
🖼️ Multiple Output Formats: Generate SVG and PNG images
🎭 Rich Themes: 67+ built-in themes including GitHub, Dracula, Monokai, and more
🪟 Window Controls: macOS-style window decorations
📏 Line Numbers: Optional line numbering
🌈 ANSI Support: Render colored terminal output
⚡ Easy API: Simple and chainable API design
🎯 Presets: 10 pre-configured styles for common use cases
🔧 Highly Customizable: Fine-tune every aspect of the output

Installation

go get github.com/landaiqing/freezelib

Quick Start

Basic Usage

package main

import (
    "os"
    "github.com/landaiqing/freezelib"
)

func main() {
    // Create a new freeze instance
    freeze := freezelib.New()

    // Go code to screenshot
    code := `package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
}`

    // Generate SVG
    svgData, err := freeze.GenerateFromCode(code, "go")
    if err != nil {
        panic(err)
    }

    // Save to file
    os.WriteFile("hello.svg", svgData, 0644)
}

Auto Language Detection

FreezeLib can automatically detect the programming language:

freeze := freezelib.New()

// Automatic language detection from code content
svgData, err := freeze.GenerateFromCodeAuto(code)

// Detect language manually
language := freeze.DetectLanguage(code)
fmt.Printf("Detected language: %s", language)

QuickFreeze API

For a more fluent experience, use the QuickFreeze API:

qf := freezelib.NewQuickFreeze()

svgData, err := qf.WithTheme("dracula").
    WithFont("Fira Code", 14).
    WithWindow().
    WithShadow().
    WithLineNumbers().
    CodeToSVGAuto(code) // Auto-detect language

API Reference

Core Types

Freeze

The main interface for generating screenshots:

freeze := freezelib.New()                    // Default config
freeze := freezelib.NewWithConfig(config)    // Custom config
freeze := freezelib.NewWithPreset("dark")    // Preset config

QuickFreeze

Simplified, chainable API:

qf := freezelib.NewQuickFreeze()
qf := freezelib.NewQuickFreezeWithPreset("terminal")

Generation Methods

From Code String

svgData, err := freeze.GenerateFromCode(code, "python")
pngData, err := freeze.GeneratePNGFromCode(code, "python")

// With automatic language detection
svgData, err := freeze.GenerateFromCodeAuto(code)
pngData, err := freeze.GeneratePNGFromCodeAuto(code)

From File

svgData, err := freeze.GenerateFromFile("main.go")
pngData, err := freeze.GeneratePNGFromFile("main.go")

From ANSI Terminal Output

terminalOutput := "\033[32mSUCCESS\033[0m: Build completed"
svgData, err := freeze.GenerateFromANSI(terminalOutput)
pngData, err := freeze.GeneratePNGFromANSI(terminalOutput)

From Reader

svgData, err := freeze.GenerateFromReader(reader, "javascript")

Configuration

Basic Configuration

config := freezelib.DefaultConfig()
config.SetTheme("github-dark")
config.SetFont("JetBrains Mono", 14)
config.SetBackground("#1e1e1e")
config.SetWindow(true)
config.SetLineNumbers(true)

Advanced Configuration

config.SetPadding(20)           // All sides
config.SetPadding(20, 40)       // Vertical, horizontal
config.SetPadding(20, 40, 20, 40) // Top, right, bottom, left

config.SetShadow(20, 0, 10)     // Blur, X offset, Y offset
config.SetBorder(1, 8, "#333")  // Width, radius, color
config.SetDimensions(800, 600)  // Width, height
config.SetLines(10, 20)         // Line range (1-indexed)

Presets

FreezeLib comes with several built-in presets:

// Available presets
presets := []string{
    "base",         // Simple, clean
    "full",         // macOS-style with window controls
    "terminal",     // Optimized for terminal output
    "presentation", // High contrast for presentations
    "minimal",      // Minimal styling
    "dark",         // Dark theme
    "light",        // Light theme
    "retro",        // Retro terminal style
    "neon",         // Neon/cyberpunk style
    "compact",      // Compact for small snippets
}

freeze := freezelib.NewWithPreset("dark")

Language Detection

FreezeLib provides powerful language detection capabilities:

freeze := freezelib.New()

// Detect language from code content
language := freeze.DetectLanguage(code)

// Detect from filename
language = freeze.DetectLanguageFromFilename("script.py")

// Combined detection (filename + content)
language = freeze.DetectLanguageFromFile("script.py", code)

// Check language support
supported := freeze.IsLanguageSupported("go")

// Get all supported languages
languages := freeze.GetSupportedLanguages()

// Custom language detector
detector := freeze.GetLanguageDetector()
detector.AddCustomMapping(".myext", "python")

Available Options

Get lists of all available options:

freeze := freezelib.New()

// Get all available options (sorted lists)
languages := freeze.GetSupportedLanguages()  // 270+ languages
themes := freeze.GetSupportedThemes()        // 67+ themes
presets := freeze.GetAvailablePresets()      // 10 presets

// Test support
isSupported := freeze.IsLanguageSupported("go")
isSupported = freeze.IsThemeSupported("github")
isValid := freezelib.IsValidPreset("dark")

// Global functions also available
languages = freezelib.GetSupportedLanguages()
themes = freezelib.GetSupportedThemes()
presets = freezelib.GetAvailablePresets()

Chainable Methods

Both Freeze and QuickFreeze support method chaining:

freeze := freezelib.New().
    WithTheme("monokai").
    WithFont("Cascadia Code", 15).
    WithWindow(true).
    WithShadow(20, 0, 10).
    WithLineNumbers(true)

svgData, err := freeze.GenerateFromCode(code, "rust")

Examples

Terminal Output Screenshot

freeze := freezelib.NewWithPreset("terminal")

ansiOutput := "\033[32m✓ Tests passed\033[0m\n" +
              "\033[31m✗ Build failed\033[0m\n" +
              "\033[33m⚠ Warning: deprecated API\033[0m"

svgData, err := freeze.GenerateFromANSI(ansiOutput)

Custom Styling

config := freezelib.DefaultConfig()
config.Theme = "github"
config.Background = "#f6f8fa"
config.Font.Family = "SF Mono"
config.Font.Size = 16
config.SetPadding(30)
config.SetMargin(20)
config.Window = true
config.ShowLineNumbers = true
config.Border.Radius = 12
config.Shadow.Blur = 25

freeze := freezelib.NewWithConfig(config)

Batch Processing

files := []string{"main.go", "config.go", "utils.go"}

for _, file := range files {
    svgData, err := freeze.GenerateFromFile(file)
    if err != nil {
        continue
    }
    
    outputFile := strings.TrimSuffix(file, ".go") + ".svg"
    os.WriteFile(outputFile, svgData, 0644)
}

Supported Languages

FreezeLib supports syntax highlighting for 270+ programming languages including:

Popular Languages

System: Go, Rust, C, C++, Zig, D, Nim, V
Web: JavaScript, TypeScript, HTML, CSS, SCSS, PHP
Enterprise: Java, C#, Kotlin, Scala, Swift
Scripting: Python, Ruby, Perl, Lua, Bash, PowerShell
Data: JSON, YAML, TOML, XML, SQL, GraphQL

Supported Themes

FreezeLib includes 67+ syntax highlighting themes:

Popular Themes

GitHub: github, github-dark
Modern: dracula, monokai, nord, one-dark
Classic: solarized-dark, solarized-light, material, vim
Colorful: colorful, friendly, fruity, rainbow_dash

Simple and Efficient

All lists are sorted alphabetically for easy browsing and selection.

Error Handling

svgData, err := freeze.GenerateFromCode(code, "go")
if err != nil {
    // Handle specific errors
    switch {
    case strings.Contains(err.Error(), "language"):
        // Language detection failed
    case strings.Contains(err.Error(), "config"):
        // Configuration error
    default:
        // Other errors
    }
}

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - see the LICENSE file for details.

Acknowledgments

This library is based on the excellent freeze CLI tool by Charm. Special thanks to the Charm team for creating such a beautiful tool.

README.md

FreezeLib - Go Library for Beautiful Code Screenshots