Agent skill

image

Generate and edit images using Nano Banana 2 (gemini-3.1-flash-image-preview, fastest) or Nano Banana Pro. Supports aspect ratio and resolution control via Google GenAI SDK.

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Install this agent skill to your Project

npx add-skill https://github.com/flight505/nano-banana/tree/main/skills/image

SKILL.md

Nano Banana - Image Generation

Overview

Generate and edit images using state-of-the-art AI models via the Google GenAI SDK. Perfect for creating visual assets, concept art, illustrations, and editing existing images.

Key Features:

  • Multiple Models: Nano Banana 2 (fast), Nano Banana Pro (quality)
  • Image Editing: Modify existing images with natural language
  • Aspect Ratio & Resolution: Control output dimensions (16:9, 4K, etc.)
  • Simple API: One command to generate or edit
  • Automatic Saving: Handles file formats automatically

When to Use This Skill

Use this skill when you need:

  • Visual Assets: Icons, illustrations, backgrounds
  • Concept Art: Ideas and visual explorations
  • Marketing Materials: Product mockups, social media images
  • Photo Editing: Modify existing images with AI
  • Creative Content: Artistic images, abstract visuals
  • Presentation Graphics: Visuals for slides and documents

Note: For technical diagrams (architecture, flowcharts, ERD), use the diagram skill instead -- it includes quality review and iteration.

Quick Start

bash
# Generate a new image
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "A beautiful sunset over mountains with orange and purple sky" -o sunset.png

# Edit an existing image
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Make the sky more dramatic with storm clouds" --input sunset.png -o dramatic_sunset.png

# Use Nano Banana Pro for highest quality
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Abstract geometric art in blue and gold" -m gemini-3-pro-image-preview -o abstract.png

Aspect Ratio & Resolution

bash
# Wide cinematic landscape
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Cinematic mountain vista" -o landscape.png --aspect-ratio 16:9

# High-resolution square image
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Product photo" -o product.png --aspect-ratio 1:1 --resolution 4K

# Ultra-wide banner
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Website hero banner" -o banner.png --aspect-ratio 21:9 --resolution 2K

# Use Nano Banana Pro for highest quality
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Professional headshot" -o headshot.png -m gemini-3-pro-image-preview

Supported aspect ratios: 1:1, 1:4, 1:8, 2:3, 3:2, 3:4, 4:1, 4:3, 4:5, 5:4, 8:1, 9:16, 16:9, 21:9 Supported resolutions: 512, 1K, 2K, 4K

Editing Existing Images

Use /nano-banana:edit to modify an existing image, or call the script directly:

bash
# Edit via command (recommended)
/nano-banana:edit sunset.png "Add dramatic storm clouds and lightning"

# Edit via script directly
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Add dramatic storm clouds" --input sunset.png -o sunset_edit1.png

When to edit vs. regenerate:

  • Edit when the base image is good but needs specific changes (add/remove elements, change colors, modify style)
  • Regenerate when the image fundamentally doesn't match what you need

Available Models

Model ID Speed Capabilities Best For
Nano Banana 2 gemini-3.1-flash-image-preview Flash (fastest) Generation + Editing Default -- high-volume, general use
Nano Banana Pro gemini-3-pro-image-preview Pro Generation + Editing Professional assets, best quality

Usage Examples

Generate New Images

bash
# Photorealistic
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Professional headshot of a business executive in modern office setting" -o headshot.png

# Artistic
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Watercolor painting of a cozy coffee shop on a rainy day" -o coffee_shop.png

# Abstract
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Abstract visualization of data flowing through neural networks, blue and cyan colors" -o neural_flow.png

# Product
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Modern minimalist logo for a tech startup called 'Nexus', clean geometric design" -o logo.png

Edit Existing Images

bash
# Change colors
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Change the car color to red" --input car.jpg -o red_car.png

# Add elements
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Add a rainbow in the sky" --input landscape.jpg -o rainbow_landscape.png

# Remove elements
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Remove the person from the background" --input photo.jpg -o clean_photo.png

# Style transfer
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Make this look like a watercolor painting" --input photo.jpg -o watercolor.png

Specify Output Format

bash
# PNG (default, best for graphics with transparency)
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Icon of a rocket ship" -o rocket.png

# Output to specific directory
python3 ${CLAUDE_SKILL_DIR}/scripts/generate_image.py "Banner image" -o assets/images/banner.png

Configuration

Google Gemini API Key (Required)

bash
export GEMINI_API_KEY='your_gemini_key_here'

Get a key at https://aistudio.google.com/apikey (free tier available).

.env File

Create a .env file in your project:

GEMINI_API_KEY=your_gemini_key_here

Python API

python
from skills.image.scripts.generate_image import generate_image

# Generate new image
result = generate_image(
    prompt="A futuristic city at night with neon lights",
    output_path="city.png",
    model="gemini-3-pro-image-preview"
)

# Edit existing image
result = generate_image(
    prompt="Add flying cars to the scene",
    output_path="city_with_cars.png",
    input_image="city.png"
)

Tips for Better Images

Be Descriptive

bash
# Too vague
"A dog"

# Detailed
"A golden retriever puppy playing in autumn leaves, warm afternoon sunlight, shallow depth of field, professional pet photography"

Include Style

bash
# Specify artistic style
"A mountain landscape in the style of traditional Japanese ink painting, minimalist, black and white with subtle gray tones"

Specify Composition

bash
# Include framing
"Close-up portrait of an owl, centered composition, soft studio lighting, dark background, sharp focus on the eyes"

For Editing, Be Specific

bash
# Vague edit
"Make it better"

# Specific edit
"Increase the contrast, make the colors more vibrant, and add a subtle vignette effect"

Comparison: image vs diagram Skills

Aspect image Skill diagram Skill
Use Case Photos, art, illustrations Technical diagrams
Quality Review No Yes (Gemini 3 Pro)
Iteration Single pass Smart iteration (1-2 passes)
Doc Types N/A 13 document types with thresholds
Image Editing Yes Yes
Best For Creative visuals Architecture, flowcharts, ERD

Rule of thumb: If it's a technical diagram with boxes, arrows, and labels, use diagram. If it's a photo, illustration, or artistic image, use image.

Troubleshooting

"GEMINI_API_KEY not found"

Set the environment variable or create a .env file. See Configuration section.

"Image file not found" (for editing)

Make sure the input image path is correct and the file exists.

Unexpected Output

  • Try a different model
  • Add more detail to your prompt
  • Be more specific about style, composition, and colors

Generation Timeout

Large or complex images may take up to 2 minutes. Timeout is set to 120 seconds.

Cost Considerations

  • Nano Banana 2 (Flash): Cheapest -- free tier available, ~$0.01-0.05 per image
  • Nano Banana Pro: ~$0.02-0.10 per image
  • Image editing: Similar to generation costs

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