Diagram Renderer

A comprehensive diagram rendering service supporting Mermaid, PlantUML, and Graphviz diagrams with an interactive web interface:

• Streamlit Dashboard - Interactive web interface for diagram rendering

Features

• Automatic diagram type detection (Mermaid, PlantUML, Graphviz)
• Self-contained rendering - All JavaScript libraries hosted locally
• Static Mermaid.js assets (version controlled, 2.8MB)
• VizJS for Graphviz/DOT rendering (locally hosted, 1.9MB)
• PlantUML to DOT conversion and rendering
• Multiple themes for Mermaid diagrams
• Interactive Streamlit dashboard, FastAPI web app, and MCP server
• No external CDN dependencies - Works offline
• AI Assistant Integration - MCP server for Claude Desktop and other AI tools

Installation

Install from PyPI:

# Using uv (recommended)
uv add diagram-renderer

# Using pip
pip install diagram-renderer

For development setup:

git clone https://github.com/djvolz/diagram-renderer.git
cd diagram-renderer
uv install

Usage

Examples

The examples/ directory contains four demonstration applications:

Streamlit Dashboard - Interactive web interface:

uv sync --extra dashboard
# Run directly
uv run --extra dashboard python -m streamlit run examples/dashboard.py
# Or use the convenience script
uv run --extra dashboard ./examples/run-dashboard.py

FastAPI Web App - REST API and web interface:

uv sync --extra webapp
uv run --extra webapp python examples/cli.py webapp
# or directly: uv run --extra webapp python examples/webapp.py

MCP Server - AI assistant integration via Model Context Protocol:

uv sync --extra mcp
uv run --extra mcp python examples/cli.py mcp
# or directly: uv run --extra mcp python examples/mcp_server.py

Command Line Interface - Batch processing and automation:

# Render diagram from file
uv run python examples/cli.py render diagram.mmd

# Quick inline rendering
uv run python examples/cli.py quick "graph TD; A-->B"

# Serve a diagram with HTTP server
uv run python examples/cli.py serve diagram.mmd

# Show examples and help
uv run python examples/cli.py examples
uv run python examples/cli.py --help

Supported Diagram Types

The visual-regression baselines cover the following diagram families:

Mermaid

• Flowchart, Sequence, Class, State, and ER diagrams
• User Journey, Timeline, Requirement, and C4 Context diagrams
• Quadrant Charts, Pie Charts, and Gantt Charts
• Git Graphs plus beta features: XY Chart, Sankey, and Block diagrams

PlantUML

• Sequence, Class, Use Case, Component, and State diagrams
• Deployment, Object, and Network diagrams

Graphviz (DOT)

• Directed and Undirected graphs, Flowcharts, and Dependency graphs
• Organizational Charts, State Machines, Network Diagrams, and Cluster diagrams

Visual Gallery

Interactive screenshots from our baseline suite are available below. Expand any section to preview the rendered output.

Mermaid Gallery

PlantUML Gallery

Graphviz Gallery

Configuration

Mermaid Themes

• default - Default theme
• base - Base theme
• dark - Dark theme
• forest - Forest theme
• neutral - Neutral theme

Development

The main components are:

• diagram_renderer/ - Core diagram rendering logic and renderers
• st_diagram.py - Streamlit diagram component wrapper
• examples/cli.py - Command-line interface and app launcher
• examples/dashboard.py - Streamlit web interface
• examples/webapp.py - FastAPI REST API and web interface
• examples/mcp_server.py - MCP server for AI assistant integration
• diagram_renderer/renderers/static/js/ - Local JavaScript libraries
  • mermaid.min.js (2.8MB) - Mermaid diagram rendering
  • viz-full.js (1.9MB) - Graphviz/DOT rendering
  • viz-lite.js (11KB) - Lightweight VizJS alternative

Demo

Input:

flowchart LR
    A[diagram-renderer] --> B{Auto-detect}
    B -->|Mermaid| C[Mermaid.js]
    B -->|PlantUML| D[PlantUML → DOT]
    B -->|Graphviz| E[VizJS]
    C --> F[Interactive HTML]
    D --> F
    E --> F
    F --> G[📱 Responsive]
    F --> H[🖼 PNG Export]
    F --> I[🔍 Zoom/Pan]

Output: The generated HTML includes:

• 🔍 Interactive zoom and pan controls
• 📱 Responsive design
• 🖼 PNG export functionality
• 🎨 Automatic diagram type detection
• 🔒 Self-contained - All JS libraries included locally (no CDN dependencies)
• ⚡ Two output modes - Lightweight external JS (14KB) or fully embedded (4.7MB)

Try it yourself:

uv run python examples/cli.py quick "graph TD; A-->B-->C"

Examples

Mermaid Flowchart

flowchart TD
    A[Start] --> B{Decision}
    B -->|Yes| C[Process A]
    B -->|No| D[Process B]
    C --> E[End]
    D --> E

PlantUML Class Diagram

@startuml
class Animal {
  +String name
  +int age
  +makeSound()
}
class Dog {
  +String breed
  +bark()
}
Animal <|-- Dog
@enduml

Graphviz DOT Diagram

digraph G {
    A -> B;
    B -> C;
    C -> A;
}