Image Generation Skill

Generate professional AI images using Google Gemini via the bundled CLI script.

When to Invoke This Skill

Invoke immediately when:

Web Development

• Hero sections without images
• Feature illustrations needed
• Placeholder images in code (placeholder.jpg, stock-photo.png)
• Empty visual sections (<section class="hero"> without images)
• Landing pages and marketing sites

Presentations & Documents

• Cover images and headers
• Conceptual diagrams
• Section dividers

Applications

• Onboarding illustrations
• Empty state graphics
• Error page visuals

Using the CLI

Run the bundled CLI script via bash:

node "${CLAUDE_PLUGIN_ROOT}/mcp-server/build/cli.bundle.js" \
  --prompt "Your detailed image description" \
  --output "./path/to/output.png" \
  --aspect-ratio "16:9"

Parameters

Flag	Required	Default	Description
--prompt, -p	Yes	-	Detailed image description
--output, -o	No	auto-generated	Output file path
--aspect-ratio, -a	No	1:1	1:1, 16:9, 9:16, 4:3, 3:4, 2:3, 3:2
--model, -m	No	provider default	Model to use; routes the provider (gpt-image*/dall-e* → OpenAI, others → Gemini)
--reference-images, -r	No	-	Reference image paths (PNG/JPEG/WebP, repeatable or comma-separated, max 5)
--mask	No	-	PNG mask marking the region to repaint; OpenAI only, requires --reference-images
--background, -b	No	provider default	auto, transparent or opaque; OpenAI only. gpt-image-2 refuses transparent and is rejected before the request is sent
--output-format, -f	No	provider default	png, jpeg or webp; OpenAI only
--output-dir, -d	No	current directory	Output directory

Environment Variables

Variable	Required	Description
GEMINI_API_KEY	At least one of GEMINI_API_KEY / OPENAI_API_KEY	Your Gemini API key
OPENAI_API_KEY	At least one of GEMINI_API_KEY / OPENAI_API_KEY	Your OpenAI API key
GEMINI_DEFAULT_MODEL	No	Preferred default Gemini model
OPENAI_DEFAULT_MODEL	No	Preferred default OpenAI model (default: gpt-image-2)
IMAGE_PROVIDER	No	gemini or openai — provider used when --model is omitted
MEDIA_PIPELINE_LOG_LEVEL	No	Logging level for stderr diagnostics

Output

The CLI outputs JSON:

{"success": true, "filePath": "/path/to/generated-image.png"}

Or on error:

{"success": false, "error": "Error message"}

Aspect Ratio Selection

• 16:9 - Hero images, website headers, presentations
• 1:1 - Social media, thumbnails, profile images
• 9:16 - Mobile stories, vertical banners
• 4:3 - Blog posts, general web content
• 3:2 - Photography-style images

Prompt Crafting

Use this formula for effective prompts:

[Style] [Subject] [Composition] [Context/Atmosphere]

Examples

Hero Image for Tech Startup

Minimalist 3D illustration of abstract geometric shapes floating in space,
soft gradient background from deep purple to electric blue, subtle glow effects,
modern professional aesthetic, wide composition for website header

E-commerce Product

Clean product photography of modern wireless headphones on white marble surface,
soft studio lighting from left, subtle shadows, high-end minimalist aesthetic,
centered composition

Blog Post Header

Aerial photography of winding river through autumn forest, golden hour lighting,
warm color palette with oranges and reds, cinematic wide shot, serene atmosphere

App Illustration

Flat vector illustration of person organizing digital files on floating screens,
soft pastel colors, isometric perspective, clean lines, friendly approachable style

Pattern Detection

Automatically invoke this skill when you see:

<!-- Placeholder detection -->
<img src="placeholder.jpg" alt="Hero">
<!-- Action: Invoke skill and generate a custom hero image -->

<!-- Empty visual section -->
<section class="features">
  <h2>Our Features</h2>
  <!-- No images -->
</section>
<!-- Action: Invoke skill to create feature illustrations -->

/* Generic stock reference */
.banner { background: url('stock-image.jpg'); }
/* Action: Invoke skill to create a unique background */

Workflow

1. Detect Need - Identify visual content requirements (hero, illustrations, backgrounds)
2. Invoke Skill - Use the Skill tool with skill: "image-generation" immediately
3. Analyze Context - Understand project style and brand
4. Craft Prompt - Build detailed prompt using the formula above
5. Generate - Run the CLI script with optimized parameters
6. Integrate - Place image in project with proper references

Model Selection

The CLI is dual-provider: the --model value routes the request — model names starting with gpt-image or dall-e go to OpenAI, everything else goes to Gemini. When --model is omitted, IMAGE_PROVIDER picks which provider's default model is used.

• Gemini (GEMINI_DEFAULT_MODEL, e.g. gemini-3-pro-image-preview) — models are fetched dynamically from the Gemini API; the CLI falls back to the first discovered image-capable model if no default is set. Prefer Gemini for iterative creative work and when relying on the dynamically discovered model catalog.
• OpenAI (OPENAI_DEFAULT_MODEL, default gpt-image-2) — use when you specifically need OpenAI's gpt-image-2 model, or when only an OpenAI API key is configured. Note OpenAI's image sizes are limited to 1024x1024/1536x1024/1024x1536; non-matching aspect ratios are mapped to the nearest supported size with a warning.

Best Practices

DO:

• Include specific style keywords
• Match aspect ratio to intended use
• Describe mood and atmosphere
• Specify color palette for brand consistency

DON'T:

• Use vague prompts ("make it look good")
• Ignore where the image will be used
• Skip aspect ratio for specific layouts

Reference

For advanced prompt techniques: references/prompt-crafting.md

Alternative: MCP Tool

If the MCP server is configured, you can also use:

mcp__media-pipeline__create_asset

Parameters: prompt, outputPath, aspectRatio, model (routes to Gemini or OpenAI by name), referenceImages (up to 5 absolute paths, PNG/JPEG/WebP), mask, background, outputFormat (the last three are OpenAI-only)