diagram-to-image

name	diagram-to-image
description	Convert Mermaid diagrams and Markdown tables to images (PNG) for platforms that don't support rich formatting. Use when user asks to "convert to image", "export as PNG", "make this an image", or has content for X/Twitter that needs visual exports.

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:

Content Pattern	Example Filename
flowchart with auth/login	auth-flow.png
sequenceDiagram with API	api-sequence.png
erDiagram	entity-relationship.png
pie chart about X	x-distribution.png
gantt chart	project-timeline.png
Table with comparison	comparison-table.png
Table with data	data-table.png

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