Nano Banana 2 Skill

AI image generation CLI powered by Gemini 3.1 Flash Image Preview (default) with support for Gemini 3 Pro and any Gemini model. Multi-resolution (512-4K), aspect ratios, cost tracking, broadcast-grade green screen transparency, reference images, and style transfer.

Also ships as a Claude Code skill for AI-assisted image generation workflows.

Install

Requirements: Bun, FFmpeg + ImageMagick (for transparent mode)

# Clone the repo
git clone https://github.com/kingbootoshi/nano-banana-2-skill.git ~/tools/nano-banana-2
cd ~/tools/nano-banana-2

# Install dependencies
bun install

# Link globally (no sudo needed - uses Bun's global bin)
bun link

# Set up your API key
mkdir -p ~/.nano-banana
echo "GEMINI_API_KEY=your_key_here" > ~/.nano-banana/.env

Get a Gemini API key at Google AI Studio.

Now you can use nano-banana from anywhere.

As a Claude Code Skill

When installed as a Claude Code skill, just say /init and Claude will clone the repo, install deps, and link the command for you. Then use it by saying "generate an image of..." and Claude handles the rest.

Fallback (if bun link doesn't work)

mkdir -p ~/.local/bin
ln -sf ~/tools/nano-banana-2/src/cli.ts ~/.local/bin/nano-banana
echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc

Usage

# Basic - generates 1K image to current directory
nano-banana "minimal dashboard UI with dark theme"

# Custom output name
nano-banana "luxury product mockup" -o product

# Higher resolution
nano-banana "detailed landscape painting" -s 2K

# Ultra high res
nano-banana "cinematic widescreen scene" -s 4K -a 16:9

# Lower resolution (fast, cheap)
nano-banana "quick sketch concept" -s 512

# Custom output directory
nano-banana "UI screenshot" -o dashboard -d ~/Pictures

Models

# Default - Nano Banana 2 (Gemini 3.1 Flash, fast and cheap)
nano-banana "your prompt"

# Pro - highest quality, 2x cost
nano-banana "your prompt" --model pro

# Any model ID
nano-banana "your prompt" --model gemini-2.5-flash-image

Alias	Model	Best For
flash, nb2	Gemini 3.1 Flash Image Preview	Speed, cost, high-volume
pro, nb-pro	Gemini 3 Pro Image Preview	Highest quality, complex composition

Aspect Ratios

# Widescreen
nano-banana "cinematic landscape" -a 16:9

# Portrait
nano-banana "mobile app screenshot" -a 9:16

# Ultra-wide
nano-banana "panoramic scene" -a 21:9

# Standard photo
nano-banana "product photo" -a 4:3

Supported: 1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3, 4:5, 5:4, 21:9

Reference Images

Edit, transform, or combine existing images:

# Edit an existing image
nano-banana "change the background to pure white" -r dark-ui.png -o light-ui

# Style transfer - multiple references
nano-banana "combine these two UI styles into one" -r style1.png -r style2.png -o combined

# Color correction
nano-banana "make this image more vibrant and increase contrast" -r photo.jpg

Transparent Assets

Generate assets with transparent backgrounds using AI-powered background removal:

# Basic transparent asset
nano-banana "robot mascot character" -t -o mascot

# Logo with transparency
nano-banana "minimalist tech logo" -t -o logo

# Game asset
nano-banana "pixel art treasure chest" -t -o chest

The -t flag automatically prompts the AI to generate on a green screen, then uses FFmpeg colorkey + despill to key out the background and remove green spill from edge pixels. ImageMagick trims the result. Requires: brew install ffmpeg imagemagick

Exact Dimensions

Control output dimensions by using a blank image as the last reference:

# First -r: your style reference
# Last -r: blank image in target dimensions
nano-banana "pixel art character, 256x256" -r style.png -r blank-256x256.png -o sprite

Options

Option	Default	Description
-o, --output	nano-gen-{timestamp}	Output filename (no extension)
-s, --size	1K	Image size: 512, 1K, 2K, or 4K
-a, --aspect	model default	Aspect ratio: 1:1, 16:9, 9:16, etc.
-m, --model	flash	Model: flash/nb2, pro/nb-pro, or any model ID
-d, --dir	current directory	Output directory
-r, --ref	-	Reference image (can use multiple times)
-t, --transparent	-	Generate on green screen, remove background (FFmpeg)
--api-key	-	Gemini API key (overrides env/file)
--costs	-	Show cost summary from generation history
-h, --help	-	Show help

Sizes and Costs

Size	Resolution	Flash Cost	Pro Cost
512	~512x512	~$0.045	N/A (Flash only)
1K	~1024x1024	~$0.067	~$0.134
2K	~2048x2048	~$0.101	~$0.201
4K	~4096x4096	~$0.151	~$0.302

Cost Tracking

Every generation logs its cost to ~/.nano-banana/costs.json. View your spending:

nano-banana --costs

Shows total generations, total spend, and per-model breakdown.

API Key Configuration

The CLI resolves the Gemini API key in priority order:

1. --api-key flag on the command line
2. GEMINI_API_KEY environment variable
3. .env file in the current working directory
4. .env file in the repo root (next to src/)
5. ~/.nano-banana/.env

Get a free key at Google AI Studio.

# Option 1: Environment variable
export GEMINI_API_KEY=your_key_here

# Option 2: .env file in current directory
echo "GEMINI_API_KEY=your_key_here" > .env

# Option 3: Global config
mkdir -p ~/.nano-banana
echo "GEMINI_API_KEY=your_key_here" > ~/.nano-banana/.env

# Option 4: Pass directly
nano-banana "your prompt" --api-key your_key_here

How Transparent Mode Works

The -t flag uses a 3-step pipeline for pixel-perfect transparency:

1. Green screen prompt - The CLI automatically appends green screen instructions to your prompt, so the AI generates on a solid green background
2. FFmpeg colorkey + despill - colorkey removes the green background. despill reconstructs edge pixel colors by mathematically removing green contamination from the RGB channels - this is why edges are clean instead of having green fringe
3. Auto-crop - ImageMagick trims transparent padding and resets canvas

The key color is auto-detected from corner pixels (the AI generates near-green like #05F904, not exact #00FF00). Requires FFmpeg and ImageMagick: brew install ffmpeg imagemagick

Use Cases

• Landing page assets - product mockups, UI previews
• Image editing - transform existing images with text prompts
• Style transfer - combine multiple reference images
• Marketing materials - hero images, feature illustrations
• UI iterations - quickly generate design variations
• Transparent assets - icons, logos, mascots with no background
• Game assets - sprites, tilesets, characters
• Video production - visual elements for Remotion/video compositions

Claude Code Skill

When installed as a Claude Code plugin, the skill triggers on phrases like:

• "generate an image"
• "create a sprite"
• "make an asset"
• "generate artwork"

Claude will construct the appropriate nano-banana command based on your request, handling model selection, resolution, aspect ratio, reference images, transparency, and output configuration automatically.

License

MIT