Nano Banana

nano-banana

AI image generation CLI. Default model: Gemini 3.1 Flash Image Preview (Nano Banana 2).

/init - First-Time Setup

When the user says "init", "setup nano-banana", or "install nano-banana", run these commands to get the CLI tool on their machine. No sudo required.

Prerequisites: Bun must be installed. If not: curl -fsSL https://bun.sh/install | bash

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

# 2. Install dependencies
cd ~/tools/nano-banana-2 && bun install

# 3. Link globally (creates `nano-banana` command via Bun - no sudo)
cd ~/tools/nano-banana-2 && bun link

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

After init, the user can type nano-banana "prompt" from anywhere.

If bun link fails or the command is not found after linking, fall back to:

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

Get a Gemini API key at: https://aistudio.google.com/apikey

Quick Reference

• Command: nano-banana "prompt" [options]
• Default: 1K resolution, Flash model, current directory

Core 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, 4:3, 3:4, 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 |

Models

| Alias | Model | Use When | |-------|-------|----------| | flash, nb2 | Gemini 3.1 Flash | Default. Fast, cheap (~$0.067/1K image) | | pro, nb-pro | Gemini 3 Pro | Highest quality needed (~$0.134/1K image) |

Sizes

| Size | Cost (Flash) | Cost (Pro) | |------|-------------|------------| | 512 | ~$0.045 | Flash only | | 1K | ~$0.067 | ~$0.134 | | 2K | ~$0.101 | ~$0.201 | | 4K | ~$0.151 | ~$0.302 |

Aspect Ratios

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

Use -a flag: nano-banana "cinematic scene" -a 16:9

Key Workflows

Basic Generation

nano-banana "minimal dashboard UI with dark theme"
nano-banana "cinematic landscape" -s 2K -a 16:9
nano-banana "quick concept sketch" -s 512

Model Selection

# Default (Flash - fast, cheap)
nano-banana "your prompt"

# Pro (highest quality)
nano-banana "detailed portrait" --model pro -s 2K

Reference Images (Style Transfer / Editing)

# Edit 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 styles" -r style1.png -r style2.png -o combined

Transparent Assets

nano-banana "robot mascot character" -t -o mascot
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. Pixel-perfect transparency with no manual prompting needed.

Requires: brew install ffmpeg imagemagick

Exact Dimensions

To get a specific output dimension:

1. First -r flag: your reference/style image
2. Last -r flag: blank image in target dimensions
3. Include dimensions in prompt

nano-banana "pixel art character in style of first image, 256x256" -r style.png -r blank-256x256.png -o sprite

Reference Order Matters

• First reference: primary style/content source
• Additional references: secondary influences
• Last reference: controls output dimensions (if using blank image trick)

Cost Tracking

Every generation is logged to ~/.nano-banana/costs.json. View summary:

nano-banana --costs

Use Cases

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

Prompt Examples

# UI mockups
nano-banana "clean SaaS dashboard with analytics charts, white background"

# Widescreen cinematic
nano-banana "cyberpunk cityscape at sunset" -a 16:9 -s 2K

# Product shots with Pro quality
nano-banana "premium software product hero image" --model pro

# Quick low-res concept
nano-banana "rough sketch of a robot" -s 512

# Dark mode UI
nano-banana "Premium SaaS chat interface, dark mode, minimal, Linear-style aesthetic"

# Game assets with transparency (green screen auto-prompted)
nano-banana "pixel art treasure chest" -t -o chest

# Portrait aspect ratio
nano-banana "mobile app onboarding screen" -a 9:16

API Key Setup

The CLI resolves the Gemini API key in this order:

1. --api-key flag
2. GEMINI_API_KEY environment variable
3. .env file in current directory
4. .env file next to the CLI script
5. ~/.nano-banana/.env

Get a key at: https://aistudio.google.com/apikey

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: kingbootoshi
• Source: kingbootoshi/nano-banana-2-skill
• License: MIT

Install and usage instructions live in the source repository linked above.