Mermaid Diagram Generator Server

A simple Flask server that generates diagrams from Mermaid syntax using mermaid-cli.

Prerequisites

Python 3.7+
Node.js and npm (for mermaid-cli)
mermaid-cli installed globally: npm install -g @mermaid-js/mermaid-cli

Installation

Clone this repository
Install Python dependencies:
```
pip install -r requirements.txt
```
Ensure mermaid-cli is installed globally:
```
npm install -g @mermaid-js/mermaid-cli
```

Running the Server

Start the server with:

python server.py

By default, the server runs on http://localhost:5000.

Temporary Files

The server creates a local directory called temp_files in the project folder for storing temporary files. This approach:

Avoids permission issues with system temp directories
Works better in virtual environments
Automatically cleans up files older than 30 minutes

API Usage

Web Interface

Open your browser and navigate to http://localhost:5000 to use the web interface.

API Endpoint

Send a POST request to /generate with a JSON body containing your Mermaid diagram:

{
  "mermaid": "graph TD\nA[Client] --> B[Load Balancer]\nB --> C[Server1]\nB --> D[Server2]",
  "theme": "default",  // optional: default, dark, forest, neutral
  "background": "white" // optional: white, transparent
}

The server will return a PNG image of the rendered diagram.

Example using curl:

curl -X POST http://localhost:5000/generate \
  -H "Content-Type: application/json" \
  -d '{"mermaid":"graph TD\nA[Client] --> B[Load Balancer]"}' \
  --output diagram.png

Testing

Run the included test script to verify everything is working:

python test.py

This will generate a sample diagram and save it as output_diagram.png.

Troubleshooting

If you encounter errors:

Ensure mermaid-cli (mmdc) is installed and accessible in your PATH
Check server logs for specific error messages
Make sure your Mermaid syntax is valid
Verify the temp_files directory exists and has appropriate permissions

Mermaid Diagram Generator