/nanobanana-skill

name: nanobanana-skill
description: 'Generate or edit images via Google Gemini (nanobanana). This is the DEFAULT image skill — use whenever the user asks to generate, create, or edit an image and does NOT name another provider. Triggers: "nanobanana", "generate image", "create image", "edit image", "图片生成", "生成图片", "AI绘图", "图片编辑". Do NOT use for diagrams (架构图/流程图/时序图) — draw those with Mermaid or code instead.'
allowed-tools: Read, Write, Glob, Grep, Task, Bash(cat:*), Bash(ls:*), Bash(tree:*), Bash(python3:*)

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 dependent packages installed**: google-genai, Pillow, python-dotenv. They could be installed via `python3 -m pip install -r ${CLAUDE_SKILL_DIR}/requirements.txt` if not installed yet. 3. **Executable**: `${CLAUDE_SKILL_DIR}/nanobanana.py`

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-3.1-flash-image-preview)
• Resolution (optional, defaults to 1K)

2. Run the nanobanana script with appropriate parameters:

   python3 ${CLAUDE_SKILL_DIR}/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 ${CLAUDE_SKILL_DIR}/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-3.1-flash-image-preview` (default) - Latest, fast generation
• `gemini-3-pro-image-preview` - Higher quality, supports thinking/reasoning

Resolution (--resolution)

• `1K` (default)
• `2K`
• `4K`

Other Options

• `--no-search` - Disable Google Search grounding (enabled by default)
• `--no-think` - Disable thinking/reasoning mode

Examples

Generate a simple image

python3 ${CLAUDE_SKILL_DIR}/nanobanana.py --prompt "A serene mountain landscape at sunset with a lake"

Generate with specific size and output

python3 ${CLAUDE_SKILL_DIR}/nanobanana.py \
  --prompt "Modern minimalist logo for a tech startup" \
  --size 1024x1024 \
  --output "logo.png"

Generate landscape image with high resolution

python3 ${CLAUDE_SKILL_DIR}/nanobanana.py \
  --prompt "Futuristic cityscape with flying cars" \
  --size 1344x768 \
  --resolution 2K \
  --output "cityscape.png"

Edit existing images

python3 ${CLAUDE_SKILL_DIR}/nanobanana.py \
  --prompt "Add a rainbow in the sky" \
  --input photo.png \
  --output "photo-with-rainbow.png"

Use pro model for higher quality

python3 ${CLAUDE_SKILL_DIR}/nanobanana.py \
  --prompt "Detailed portrait of a cat in watercolor style" \
  --model gemini-3-pro-image-preview \
  --output "cat-portrait.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-3.1-flash-image-preview (default) for speed