Flowmaid.py

Flowmaid.py is a pure Python library designed to convert Mermaid flowcharts into clean, styled SVG files. It serves as a lightweight, zero-dependency alternative to the JavaScript-based mermaid.js for flowchart rendering.

Features

• Zero Dependencies: Uses only the Python standard library.
• Single File: The entire library is contained in Flowmaid.py.
• Mermaid Syntax Support:
  • graph and flowchart headers.
  • Directions: TD (Top-Down) and LR (Left-Right).
  • Node Shapes: Rectangular [], Rounded (), Diamond {}, Circle (()), Cylinder [()], and Rhomboid >].
  • Edge Types: Normal -->, Thick ==>, Dotted -.->, and Link ---.
  • Labeled Edges: A -- label --> B or A -->|label| B.
• Advanced Styling:
  • style command for node colors, borders, and widths.
  • linkStyle command for individual edge customization.
• Subgraphs: Support for subgraph blocks with custom labels and visual grouping.
• Layout & Rendering:
  • BFS-based hierarchical ranking for stable positioning.
  • Dynamic node sizing based on label length.
  • Automatic text wrapping for long labels.
  • Precise arrowheads that point exactly to node boundaries.

Installation

Simply copy Flowmaid.py into your project. No pip install required!

Usage

Command Line

You can generate an SVG directly from a Mermaid file:

python3 Flowmaid.py flowchart.mermaid > flowchart.svg

Python API

You can also use Flowmaid.py within your Python scripts:

from Flowmaid import Flowmaid

mermaid_code = """
graph TD
    subgraph SG1[Main Process]
        A[Start] --> B{Is it working?}
        B -- Yes --> C[Great!]
        B -- No --> D[Fix it]
    end
    C --> E[End]
    D --> B
    style A fill:#f9f,stroke:#333,stroke-width:4px
    linkStyle 0 stroke:#ff3,stroke-width:4px
"""

mp = Flowmaid(mermaid_code)
svg_output = mp.generate_svg()

with open("output.svg", "w") as f:
    f.write(svg_output)

Example Output

The library handles complex layouts and ensures that styles are correctly applied as inline SVG attributes for maximum compatibility across different viewers.

Future Plans

• Support for nested subgraphs.
• Multi-directional edges (<-->).
• Support for other Mermaid diagram types (Sequence, Gantt, etc.).
• Improved edge routing to minimize crossovers.