Diagram to Image

Convert Mermaid diagrams and Markdown tables to PNG images via the mermaid-red API (diagramless.xyz). Produces high-quality, styled output with custom themes — no heavy local dependencies needed.

When to Use

Use this skill when:

• User has a Mermaid diagram that needs to be converted to an image
• User has a Markdown table that needs to be converted to an image
• User is writing content for X/Twitter and needs visual exports
• User asks to "convert to image", "export as PNG", "make this an image", or similar

Prerequisites

The bundled script uses Node.js built-in fetch (Node 18+). No npm install needed.

# The render script is bundled with this skill:
SKILL_DIR=~/.claude/skills/diagram-to-image/scripts
ls $SKILL_DIR/diagram-to-image.mjs

Smart Output Location

IMPORTANT: Determine the best output location based on context. Follow this decision tree:

1. User Specifies Path

If user explicitly mentions a path or filename, use that.

2. Project Context Detection

Check for common image/asset directories in the current project:

# Check for existing image directories (in order of preference)
ls -d ./images ./assets ./img ./static ./public/images ./assets/images 2>/dev/null | head -1

Use the first existing directory found. Common patterns:

• ./images/ - General projects
• ./assets/ - Web projects
• ./assets/images/ - Structured web projects
• ./public/images/ - Next.js, React projects
• ./static/ - Hugo, other static site generators
• ./img/ - Short form convention

3. Article/Document Context

If user is writing an article or document:

• Look for the document's directory
• Create images/ subdirectory if appropriate
• Name the image based on the document name + descriptor

4. Conversation Context

Analyze the conversation to determine:

• What the diagram represents → Use for filename (e.g., auth-flow.png, user-journey.png)
• Related file being discussed → Place image near that file
• Topic being discussed → Use for naming

5. Default Fallback

If no context clues:

• Use current working directory
• Generate descriptive filename from diagram content

Filename Generation

Create meaningful filenames based on content analysis:

Rules:

• Use kebab-case (lowercase with hyphens)
• Keep names concise but descriptive (2-4 words)
• Avoid generic names like diagram.png or image.png
• Include topic/subject when identifiable

Conversion Process

Step 1: Analyze Context

Before converting, gather context:

1. Check current working directory
2. Look for existing image directories
3. Analyze diagram/table content for naming
4. Consider any files or topics mentioned in conversation

Step 2: Determine Output Path

# Example logic (implement mentally, not as literal script)
if user_specified_path:
    output_path = user_specified_path
elif exists("./images"):
    output_path = "./images/{generated_name}.png"
elif exists("./assets"):
    output_path = "./assets/{generated_name}.png"
elif exists("./public/images"):
    output_path = "./public/images/{generated_name}.png"
else:
    output_path = "./{generated_name}.png"

Step 3: Create Temporary Input File

# For Mermaid diagrams
cat > /tmp/diagram.mmd << 'DIAGRAM_EOF'
<mermaid content>
DIAGRAM_EOF

# For Markdown tables
cat > /tmp/table.md << 'TABLE_EOF'
<table content>
TABLE_EOF

Step 4: Convert via mermaid-red API

The API auto-detects content type (mermaid vs table). Both use the same command.

Using the bundled script:

# Mermaid diagram
node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/diagram.mmd -o <output_path>.png

# Markdown table
node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/table.md -o <output_path>.png

# With custom theme
node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/diagram.mmd -o <output_path>.png --theme ocean

# Force content type (if auto-detect gets it wrong)
node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/table.md -o <output_path>.png --type table

Available options:

• --theme <name> — default, dark, forest, neutral, ocean, emerald, midnight, slate, lavender, blueprint
• --type <type> — auto (default), mermaid, table
• --scale <n> — 1-4 (default: 2, for 2x DPI)
• --bg <color> — Background color (default: white, use "transparent" for no bg)
• --server <url> — Override server (default: https://diagramless.xyz)

Piping from stdin also works:

echo "graph TD; A-->B" | node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs -o out.png
cat /tmp/table.md | node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs --type table -o table.png

Step 5: Report Result

After conversion, tell the user:

1. Full path where image was saved
2. Why that location was chosen (briefly)
3. File size in bytes (printed by the script)
4. Suggest they can specify a different location if needed

Examples

Example 1: Project with images/ directory

Context: User is in a project that has ./images/ directory, discussing authentication.

User: "Convert this to an image"

flowchart TD
    A[Login] --> B{Valid?}
    B -->|Yes| C[Dashboard]
    B -->|No| D[Error]

Action:

1. Detect ./images/ exists
2. Analyze content → authentication flow
3. Generate filename: login-flow.png
4. Save content to /tmp/diagram.mmd
5. Run: node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/diagram.mmd -o ./images/login-flow.png

Example 2: Writing X article about AI with ocean theme

Context: User mentioned writing an article about AI agents for X.

User: "Make this a PNG with ocean theme"

flowchart LR
    User --> Agent --> Tools --> Response

Action:

1. Save content to /tmp/diagram.mmd
2. Run: node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/diagram.mmd -o ./ai-agent-flow.png --theme ocean

Example 3: Data comparison table

User: "Export this table as image"

| Model | Speed | Accuracy |
|-------|-------|----------|
| GPT-4 | Slow | High |
| Claude | Fast | High |

Action:

1. Save content to /tmp/table.md
2. Run: node ~/.claude/skills/diagram-to-image/scripts/diagram-to-image.mjs /tmp/table.md -o ./model-comparison.png

(auto-detects as table)

Example 4: User specifies location

User: "Save this diagram to ~/Desktop/my-chart.png"

Action: Use exactly ~/Desktop/my-chart.png as output path.

Error Handling

• If the API server is unreachable, the script prints a clear error message
• If content type auto-detection fails, use --type mermaid or --type table explicitly
• For local development/testing, use --server http://localhost:3000