Pretty Mermaid

Render stunning, professionally-styled Mermaid diagrams with one command. Supports SVG for web/docs and ASCII for terminals.

Quick Start

Render a Single Diagram

From a file:

node scripts/render.mjs \
  --input diagram.mmd \
  --output diagram.svg \
  --format svg \
  --theme tokyo-night

From user-provided Mermaid code:

Save the code to a .mmd file
Run the render script with desired theme

Batch Render Multiple Diagrams

node scripts/batch.mjs \
  --input-dir ./diagrams \
  --output-dir ./output \
  --format svg \
  --theme dracula \
  --workers 4

ASCII Output (Terminal-Friendly)

node scripts/render.mjs \
  --input diagram.mmd \
  --format ascii \
  --use-ascii

Workflow Decision Tree

Step 1: What does the user want?

Render existing Mermaid code → Go to Rendering
Create new diagram → Go to Creating
Apply/change theme → Go to Theming
Batch process → Go to Batch Rendering

Step 2: Choose output format

SVG (web, docs, presentations) → --format svg
ASCII (terminal, logs, plain text) → --format ascii

Step 3: Select theme

Dark mode docs → tokyo-night (recommended)
Light mode docs → github-light
Vibrant colors → dracula
See all themes → Run node scripts/themes.mjs

Rendering Diagrams

From File

When user provides a .mmd file or Mermaid code block:

Save to file (if code block):

cat > diagram.mmd << 'EOF'
flowchart LR
    A[Start] --> B[End]
EOF

Render with theme:

node scripts/render.mjs \
  --input diagram.mmd \
  --output diagram.svg \
  --theme tokyo-night

Verify output:
- SVG: Open in browser or embed in docs
- ASCII: Display in terminal

Output Formats

SVG (Scalable Vector Graphics)

Best for: Web pages, documentation, presentations
Features: Full color support, transparency, scalable
Usage: --format svg --output diagram.svg

ASCII (Terminal Art)

Best for: Terminal output, plain text logs, README files
Features: Pure text, works anywhere, no dependencies
Usage: --format ascii (prints to stdout)
Options:
- --use-ascii - Use pure ASCII (no Unicode)
- --padding-x 5 - Horizontal spacing
- --padding-y 5 - Vertical spacing

Advanced Options

Custom Colors (overrides theme):

node scripts/render.mjs \
  --input diagram.mmd \
  --bg "#1a1b26" \
  --fg "#a9b1d6" \
  --accent "#7aa2f7" \
  --output custom.svg

Transparent Background:

node scripts/render.mjs \
  --input diagram.mmd \
  --transparent \
  --output transparent.svg

Custom Font:

node scripts/render.mjs \
  --input diagram.mmd \
  --font "JetBrains Mono" \
  --output custom-font.svg

Creating Diagrams

Using Templates

Step 1: List available templates

ls assets/example_diagrams/
# flowchart.mmd  sequence.mmd  state.mmd  class.mmd  er.mmd

Step 2: Copy and modify

cp assets/example_diagrams/flowchart.mmd my-workflow.mmd
# Edit my-workflow.mmd with user requirements

Step 3: Render

node scripts/render.mjs \
  --input my-workflow.mmd \
  --output my-workflow.svg \
  --theme github-dark

Diagram Type Reference

For detailed syntax and best practices, see DIAGRAM_TYPES.md.

Quick reference:

Flowchart - Processes, workflows, decision trees

flowchart LR
    A[Start] --> B{Decision}
    B -->|Yes| C[Action]
    B -->|No| D[End]

Sequence - API calls, interactions, message flows

sequenceDiagram
    User->>Server: Request
    Server-->>User: Response

State - Application states, lifecycle, FSM

stateDiagram-v2
    [*] --> Idle
    Idle --> Loading
    Loading --> [*]

Class - Object models, architecture, relationships

classDiagram
    User --> Post: creates
    Post --> Comment: has

ER - Database schema, data models

erDiagram
    USER ||--o{ ORDER : places
    ORDER ||--|{ ORDER_ITEM : contains

From User Requirements

Step 1: Identify diagram type

Process/workflow → Flowchart
API/interaction → Sequence
States/lifecycle → State
Object model → Class
Database → ER

Step 2: Create diagram file

cat > user-diagram.mmd << 'EOF'
# [Insert generated Mermaid code]
EOF

Step 3: Render and iterate

node scripts/render.mjs \
  --input user-diagram.mmd \
  --output preview.svg \
  --theme tokyo-night

# Review with user, edit diagram.mmd if needed, re-render

Theming

List Available Themes

node scripts/themes.mjs

Output:

Available Beautiful-Mermaid Themes:

 1. zinc-light
 2. zinc-dark
 3. tokyo-night
 4. tokyo-night-storm
 5. tokyo-night-light
 6. catppuccin-mocha
 7. catppuccin-latte
 8. nord
 9. nord-light
10. dracula
11. github-dark
12. github-light
13. solarized-dark
14. solarized-light
15. one-dark

Total: 15 themes

Theme Selection Guide

For dark mode documentation:

tokyo-night ⭐ - Modern, developer-friendly
github-dark - Familiar GitHub style
dracula - Vibrant, high contrast
nord - Cool, minimalist

For light mode documentation:

github-light - Clean, professional
zinc-light - High contrast, printable
catppuccin-latte - Warm, friendly

Detailed theme information: See THEMES.md

Apply Theme to Diagram

node scripts/render.mjs \
  --input diagram.mmd \
  --output themed.svg \
  --theme tokyo-night

Compare Themes

Render the same diagram with multiple themes:

for theme in tokyo-night dracula github-dark; do
  node scripts/render.mjs \
    --input diagram.mmd \
    --output "diagram-${theme}.svg" \
    --theme "$theme"
done

Batch Rendering

Batch Render Directory

Step 1: Organize diagrams

diagrams/
├── architecture.mmd
├── workflow.mmd
└── database.mmd

Step 2: Batch render

node scripts/batch.mjs \
  --input-dir ./diagrams \
  --output-dir ./rendered \
  --format svg \
  --theme tokyo-night \
  --workers 4

Output:

Found 3 diagram(s) to render...
✓ architecture.mmd
✓ workflow.mmd
✓ database.mmd

3/3 diagrams rendered successfully

Batch with Multiple Formats

Render both SVG and ASCII:

# SVG for docs
node scripts/batch.mjs \
  --input-dir ./diagrams \
  --output-dir ./svg \
  --format svg \
  --theme github-dark

# ASCII for README
node scripts/batch.mjs \
  --input-dir ./diagrams \
  --output-dir ./ascii \
  --format ascii \
  --use-ascii

Performance Options

--workers N - Parallel rendering (default: 4)
Recommended: --workers 8 for 10+ diagrams

Common Use Cases

1. Architecture Diagram for Documentation

# User provides architecture description
# → Create flowchart.mmd
# → Render with professional theme

node scripts/render.mjs \
  --input architecture.mmd \
  --output docs/architecture.svg \
  --theme github-dark \
  --transparent

2. API Sequence Diagram

# User describes API flow
# → Create sequence.mmd
# → Render with clear theme

node scripts/render.mjs \
  --input api-flow.mmd \
  --output api-sequence.svg \
  --theme tokyo-night

3. Database Schema Visualization

# User provides table definitions
# → Create er.mmd
# → Render for database docs

node scripts/render.mjs \
  --input schema.mmd \
  --output database-schema.svg \
  --theme dracula

4. Terminal-Friendly Workflow

# For README or terminal display
node scripts/render.mjs \
  --input workflow.mmd \
  --format ascii \
  --use-ascii > workflow.txt

5. Presentation Slides

# High-contrast for projectors
node scripts/render.mjs \
  --input slides-diagram.mmd \
  --output presentation.svg \
  --theme zinc-light

Troubleshooting

beautiful-mermaid Not Installed

Error: Cannot find module 'beautiful-mermaid'

Note: This should auto-install on first run. If it fails:

cd /path/to/pretty-mermaid-skill && npm install

Invalid Mermaid Syntax

Error: Parse error on line 3

Solution:

Validate syntax against DIAGRAM_TYPES.md
Test on https://mermaid.live/
Check for common errors:
- Missing spaces in A --> B
- Incorrect node shape syntax
- Unclosed brackets

File Not Found

Error: Input file not found: diagram.mmd

Solution: Verify file path is correct, use absolute path if needed

Resources

scripts/

Executable Node.js scripts for rendering operations:

render.mjs - Main rendering script
batch.mjs - Batch processing script
themes.mjs - Theme listing utility

references/

Documentation to inform diagram creation:

THEMES.md - Detailed theme reference with examples
DIAGRAM_TYPES.md - Comprehensive syntax guide for all diagram types
api_reference.md - beautiful-mermaid API documentation

assets/

Template files for quick diagram creation:

example_diagrams/flowchart.mmd - Flowchart template
example_diagrams/sequence.mmd - Sequence diagram template
example_diagrams/state.mmd - State diagram template
example_diagrams/class.mmd - Class diagram template
example_diagrams/er.mmd - ER diagram template

Tips & Best Practices

Performance

Batch render for 3+ diagrams (parallel processing)
Keep diagrams under 50 nodes for fast rendering
Use ASCII for quick previews

Quality

Use tokyo-night or github-dark for technical docs
Add transparency for dark/light mode compatibility: --transparent
Test theme in target environment before batch rendering

Workflow

Start with templates from assets/example_diagrams/
Iterate with user feedback
Apply theme last
Render both SVG (docs) and ASCII (README) if needed

Accessibility

Use high-contrast themes for presentations
Add text labels to all connections
Avoid color-only information encoding