Nano Banana Skill

Image generation, editing, and restoration powered by Google Gemini.

Setup (One-Time)

Before first use, set up the Python environment and API key:

# 1. Create virtual environment and install dependencies
cd <skill-dir>/scripts
python3 -m venv venv
./venv/bin/pip install -r requirements.txt

# 2. Set API key (get one at https://aistudio.google.com/apikey)
export GEMINI_API_KEY="your-api-key"

The API key can be set as any of these environment variables (checked in order): NANOBANANA_GEMINI_API_KEY, NANOBANANA_GOOGLE_API_KEY, GEMINI_API_KEY, GOOGLE_API_KEY

Quick Reference

Generate Images

Create images from text prompts:

# Basic generation
python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "A banana floating in space"

# With specific size and format
python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "Cyberpunk cityscape at night" --size 2K --format jpeg

# With explicit output path
python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "Minimalist logo" --output ./my-logo.png

When --output is omitted, files are saved to ./nanobanana-output/ with auto-generated names based on the prompt.

Edit Images

Modify existing images using natural language instructions:

# Change style
python3 <skill-dir>/scripts/nanobanana.py --mode edit --input photo.jpg --prompt "Convert to watercolor painting style"

# Modify content
python3 <skill-dir>/scripts/nanobanana.py --mode edit --input scene.png --prompt "Add a rainbow in the sky"

# Change colors
python3 <skill-dir>/scripts/nanobanana.py --mode edit --input logo.png --prompt "Change the color scheme to blue and gold"

Restore Images

Enhance, repair, or upscale images:

# Auto-restore (uses default restoration prompt)
python3 <skill-dir>/scripts/nanobanana.py --mode restore --input old_photo.jpg

# Targeted restoration
python3 <skill-dir>/scripts/nanobanana.py --mode restore --input damaged.png --prompt "Remove scratches and improve sharpness"

# Enhance quality
python3 <skill-dir>/scripts/nanobanana.py --mode restore --input blurry.jpg --prompt "Enhance clarity and increase detail" --size 4K

Reference Images

Use reference images to guide the style of generated images:

# Single reference
python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "A mountain landscape" --reference style_guide.png

# Multiple references
python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "Product photo" --reference brand_style.png --reference color_palette.png

The script searches for input and reference files in these locations:

• Current directory
• ./images/
• ./input/
• ./nanobanana-output/
• ~/Downloads/
• ~/Desktop/

Output

Smart Naming

When --output is omitted, files are automatically named based on the prompt text:

• Prompt is converted to lowercase with special characters removed
• Spaces become underscores, limited to 32 characters
• Duplicate names get a numeric suffix (_1, _2, etc.)
• All auto-named files go into ./nanobanana-output/

Sizes

Model Selection

Set the NANOBANANA_MODEL environment variable to choose a model:

# Default model (fast, good quality)
export NANOBANANA_MODEL="gemini-2.5-flash-image"

# Pro model (highest quality)
export NANOBANANA_MODEL="gemini-3-pro-image-preview"

If unset, defaults to gemini-2.5-flash-image.

Specialized Patterns

No special flags are needed for these — just use descriptive prompts:

Icons

python3 <skill-dir>/scripts/nanobanana.py --mode generate \
  --prompt "Flat design app icon for a weather app, rounded corners, minimal style, solid background" \
  --size 1K

Patterns

python3 <skill-dir>/scripts/nanobanana.py --mode generate \
  --prompt "Seamless tileable geometric pattern, blue and white, high density, suitable for fabric print"

Diagrams

python3 <skill-dir>/scripts/nanobanana.py --mode generate \
  --prompt "Architecture diagram showing microservices: API gateway, auth service, user service, database. Clean lines, labeled boxes"

Sequential / Story Images

Generate each frame as a separate call, referencing previous outputs to maintain visual consistency:

# Frame 1
python3 <skill-dir>/scripts/nanobanana.py --mode generate \
  --prompt "Scene 1 of 3: A hero stands at the edge of a forest, sunrise, cinematic style" \
  --output ./nanobanana-output/story_1.png

# Frame 2 (reference previous for consistency)
python3 <skill-dir>/scripts/nanobanana.py --mode generate \
  --prompt "Scene 2 of 3: The same hero enters the forest, dappled light, cinematic style" \
  --reference ./nanobanana-output/story_1.png \
  --output ./nanobanana-output/story_2.png

Preview

Add --preview to automatically open the generated image:

python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "Sunset over ocean" --preview

Uses the system default image viewer (macOS: open, Linux: xdg-open, Windows: start).

JSON Output

Add --json for structured output suitable for agent parsing:

python3 <skill-dir>/scripts/nanobanana.py --mode generate --prompt "A banana" --json

Output format:

{
  "success": true,
  "files": ["nanobanana-output/a_banana.png"],
  "message": "Image generated successfully."
}

On failure:

{
  "success": false,
  "files": [],
  "message": "Error description here"
}

Error Handling

See references/ADVANCED.md for advanced prompt engineering patterns, model comparison, and troubleshooting.