Code Renderer

A fast, customizable code-to-image rendering API built in Rust. Generate beautiful PNG or SVG images of syntax-highlighted code snippets with extensive theming options.

Features

• Syntax Highlighting: 50+ languages supported via syntect
• Multiple Output Formats: PNG (with configurable scale) and SVG
• Extensive Customization:
  • Multiple built-in themes
  • Override individual syntax token colors (keywords, strings, comments, etc.)
  • Customizable padding, border radius, and shadows
  • macOS or Windows-style window controls
  • Line numbers with configurable start
  • Line highlighting
• High Quality: Retina-ready PNG output with configurable scale factor
• Fast: Built with Axum for high-performance async HTTP

Quick Start

Using Docker

docker build -t code-renderer .
docker run -p 3000:3000 code-renderer

From Source

cargo build --release
./target/release/code-renderer

The server starts on http://localhost:3000.

You can configure the listen address and port via CLI flags:

• --addr <ADDR> (default: 0.0.0.0)
• --port <PORT> (default: 3000)

Examples:

./target/release/code-renderer --addr 127.0.0.1 --port 8080
./target/release/code-renderer --port 4000

API Reference

POST /render

Render code to an image.

Request Body:

{
  "code": "fn main() {\n    println!(\"Hello, world!\");\n}",
  "language": "rust",
  "output_format": "png",
  "scale": 2,
  "theme": "base16-ocean.dark",
  "title": "main.rs",
  "line_numbers": true,
  "line_number_start": 1,
  "highlight_lines": [2],
  "font_family": "Menlo",
  "font_size": 14,
  "line_height": 1.5,
  "padding": {
    "top": 20,
    "right": 24,
    "bottom": 24,
    "left": 24
  },
  "border_radius": 12,
  "shadow": {
    "enabled": true,
    "color": "rgba(0, 0, 0, 0.55)",
    "blur": 60,
    "offset_x": 0,
    "offset_y": 20
  },
  "window_controls": {
    "enabled": true,
    "style": "macos"
  },
  "theme_overrides": {
    "background": "#1e1e2e",
    "keyword": "#cba6f7",
    "string": "#a6e3a1"
  }
}

Response: PNG or SVG image data

GET /themes

List available syntax themes.

Response:

{
  "themes": ["base16-ocean.dark", "base16-ocean.light", "Solarized (dark)", ...]
}

GET /languages

List supported programming languages.

Response:

{
  "languages": ["Rust", "Python", "JavaScript", "Go", ...]
}

GET /health

Health check endpoint. Returns 200 OK.

Configuration Options

Basic Options

Option	Type	Default	Description
code	string	required	Source code to render
language	string	required	Language for syntax highlighting
output_format	"png" | "svg"	"png"	Output format
scale	number	2.0	Scale factor for PNG (2.0 = retina)
theme	string	"base16-ocean.dark"	Base syntax theme
title	string	null	Window title text

Typography

Option	Type	Default	Description
font_family	string	"Menlo"	Font family (system font)
font_size	number	14	Font size in pixels
line_height	number	1.5	Line height multiplier
line_numbers	boolean	true	Show line numbers
line_number_start	number	1	Starting line number
highlight_lines	number[]	[]	Lines to highlight (1-indexed)

Layout

Option	Type	Default	Description
padding.top	number	20	Top padding in pixels
padding.right	number	24	Right padding
padding.bottom	number	24	Bottom padding
padding.left	number	24	Left padding
border_radius	number	12	Corner radius
width	number	null	Fixed width (auto if null)
max_width	number	800	Maximum width

Shadow

Option	Type	Default	Description
shadow.enabled	boolean	true	Enable drop shadow
shadow.color	string	"rgba(0,0,0,0.55)"	Shadow color
shadow.blur	number	60	Blur radius
shadow.offset_x	number	0	Horizontal offset
shadow.offset_y	number	20	Vertical offset

Window Controls

Option	Type	Default	Description
window_controls.enabled	boolean	true	Show window controls
window_controls.style	"macos" | "windows"	"macos"	Control style

Theme Overrides

Override any color in the theme:

Option	Description
theme_overrides.background	Background color
theme_overrides.foreground	Default text color
theme_overrides.line_numbers	Line number color
theme_overrides.title	Title text color
theme_overrides.line_highlight	Highlighted line background
theme_overrides.keyword	Keywords (fn, let, if, etc.)
theme_overrides.string	String literals
theme_overrides.comment	Comments
theme_overrides.function	Function names
theme_overrides.type	Type names
theme_overrides.number	Number literals
theme_overrides.operator	Operators
theme_overrides.variable	Variable names
theme_overrides.punctuation	Punctuation
theme_overrides.window_controls	Custom window control colors

Examples

Basic Usage

curl -X POST http://localhost:3000/render \
  -H "Content-Type: application/json" \
  -d '{
    "code": "fn main() {\n    let name = \"World\";\n    let count: i32 = 42;\n    // Print greeting\n    println!(\"Hello, {}! Count: {}\", name, count);\n}",
    "language": "rust",
    "output_format": "svg",
    "theme_overrides": {
      "background": "#1e1e2e",
      "foreground": "#cdd6f4",
      "line_numbers": "#6c7086",
      "title": "#bac2de",
      "keyword": "#cba6f7",
      "string": "#a6e3a1",
      "comment": "#6c7086",
      "function": "#89b4fa",
      "type": "#f9e2af",
      "number": "#fab387",
      "operator": "#89dceb",
      "variable": "#cdd6f4",
      "punctuation": "#9399b2"
    },
    "title": "main.rs",
    "scale": 1,
    "border_radius": 0
  }' -o code.svg

Available Themes

• base16-ocean.dark
• base16-ocean.light
• base16-eighties.dark
• base16-mocha.dark
• Solarized (dark)
• Solarized (light)
• InspiredGitHub

Use GET /themes for the complete list.

Supported Languages

50+ languages including:

• Rust, Go, Python, JavaScript, TypeScript
• C, C++, C#, Java, Kotlin
• Ruby, PHP, Swift, Objective-C
• HTML, CSS, JSON, YAML, XML
• SQL, Shell/Bash, Dockerfile
• And many more...

Use GET /languages for the complete list.

Environment Variables

Variable	Default	Description
PORT	3000	Server port
RUST_LOG	code_renderer=info	Log level

Development

# Run in development mode with hot reload
cargo watch -x run

# Run tests
cargo test

# Build release binary
cargo build --release

License

MIT