Nanobanana Image Generation Skill

Generate or edit images using Google Gemini API through the nanobanana tool.

Requirements

1. GEMINI_API_KEY: Must be configured in ~/.nanobanana.env or export GEMINI_API_KEY=<your-api-key>
2. Python3 with depedent packages installed: google-genai, Pillow, python-dotenv. They could be installed via python3 -m pip install -r ~/.codex/skills/nanobanana-skill/requirements.txt if not installed yet.
3. Executable: ~/.codex/skills/nanobanana-skill/nanobanana.py

Example .nanobanana.env:

GEMINI_API_KEY=sk-dummy

Instructions

For image generation

1. Ask the user for:

   • What they want to create (the prompt)
   • Desired aspect ratio/size (optional, defaults to 9:16 portrait)
   • Output filename (optional, auto-generates UUID if not specified)
   • Model preference (optional, defaults to gemini-3-pro-image-preview)
   • Resolution (optional, defaults to 1K)

2. Run the nanobanana script with appropriate parameters:

   python3 ~/.codex/skills/nanobanana-skill/nanobanana.py --prompt "description of image" --output "filename.png"
   

3. Show the user the saved image path when complete

For image editing

1. Ask the user for:

   • Input image file(s) to edit
   • What changes they want (the prompt)
   • Output filename (optional)

2. Run with input images:

   python3 ~/.codex/skills/nanobanana-skill/nanobanana.py --prompt "editing instructions" --input image1.png image2.png --output "edited.png"
   

Available Options

Aspect Ratios (--size)

• 1024x1024 (1:1) - Square
• 832x1248 (2:3) - Portrait
• 1248x832 (3:2) - Landscape
• 864x1184 (3:4) - Portrait
• 1184x864 (4:3) - Landscape
• 896x1152 (4:5) - Portrait
• 1152x896 (5:4) - Landscape
• 768x1344 (9:16) - Portrait (default)
• 1344x768 (16:9) - Landscape
• 1536x672 (21:9) - Ultra-wide

Models (--model)

• gemini-3-pro-image-preview (default) - Higher quality
• gemini-2.5-flash-image - Faster generation

Resolution (--resolution)

• 1K (default)
• 2K
• 4K

Optional Flags

• --enable-google-search Enable Google Search tool for the model (default: disabled)
• --include-thoughts Include model thinking in output (default: disabled)

Examples

Generate a simple image

python3 ~/.codex/skills/nanobanana-skill/nanobanana.py --prompt "A serene mountain landscape at sunset with a lake"

Generate with specific size and output

python3 ~/.codex/skills/nanobanana-skill/nanobanana.py \
  --prompt "Modern minimalist logo for a tech startup" \
  --size 1024x1024 \
  --output "logo.png"

Generate landscape image with high resolution

python3 ~/.codex/skills/nanobanana-skill/nanobanana.py \
  --prompt "Futuristic cityscape with flying cars" \
  --size 1344x768 \
  --resolution 2K \
  --output "cityscape.png"

Edit existing images

python3 ~/.codex/skills/nanobanana-skill/nanobanana.py \
  --prompt "Add a rainbow in the sky" \
  --input photo.png \
  --output "photo-with-rainbow.png"

Use faster model

python3 ~/.codex/skills/nanobanana-skill/nanobanana.py \
  --prompt "Quick sketch of a cat" \
  --model gemini-2.5-flash-image \
  --output "cat-sketch.png"

Error Handling

If the script fails:

• Check that GEMINI_API_KEY is exported or set in ~/.nanobanana.env
• Verify input image files exist and are readable
• Ensure the output directory is writable
• If no image is generated, try making the prompt more specific about wanting an image

Best Practices

1. Be descriptive in prompts - include style, mood, colors, composition
2. For logos/graphics, use square aspect ratio (1024x1024)
3. For social media posts, use 9:16 for stories or 1:1 for posts
4. For wallpapers, use 16:9 or 21:9
5. Start with 1K resolution for testing, upgrade to 2K/4K for final output
6. Use gemini-3-pro-image-preview for best quality, gemini-2.5-flash-image for speed