nanobanana

name	nanobanana
description	Generate and edit images using Google Gemini or OpenAI GPT Image models. Automatically used for requests like "generate an image", "create an illustration", "edit this image". Also supports sticker sheet generation and splitting for requests like "create some stickers" or "generate multiple icons and split them". Choose between Gemini (Nano Banana) and OpenAI (gpt-image-1.5) providers.
allowed-tools	Bash, Read, Write, AskUserQuestion

Nano Banana Image Generation Skill

Generate and edit images using Google Gemini or OpenAI GPT Image.

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Referencing Pasted Images

When images are pasted into Claude Code, they are cached at ~/.claude/image-cache/. Copy from this cache to tmp and use as reference image.

How to Get Image Path (Recommended)

Important: When an image is pasted, always save it to tmp before using.

1. User pastes an image
2. Check the image-cache path from Additional working directories in environment info
   • Example: /Users/username/.claude/image-cache/0353f5a1-9885-4743-a956-d2d195b445d4
3. Copy the image file from that directory to tmp
4. Pass the tmp path to the -r option

Command to Save Image to tmp

# 1. Check image-cache path (from Additional working directories in environment info)
# Example: /Users/username/.claude/image-cache/0353f5a1-9885-4743-a956-d2d195b445d4

# 2. Check images in cache
ls ~/.claude/image-cache/<session-id>/

# 3. Copy to tmp
cp ~/.claude/image-cache/<session-id>/*.png /tmp/reference_image.png

# 4. Use as reference image
python3 ~/.claude/skills/nanobanana/generate.py "Same style. Object: cat" \
  -r "/tmp/reference_image.png" -o cat.png

Example: Generate Using Pasted Image as Reference

# 1. Copy latest image from image-cache to tmp
cp ~/.claude/image-cache/0353f5a1-9885-4743-a956-d2d195b445d4/3.png /tmp/reference_image.png

# 2. Gemini: Copy reference image style
python3 ~/.claude/skills/nanobanana/generate.py "Same style. Object: cat" \
  -r "/tmp/reference_image.png" -o cat.png

# 3. OpenAI: Edit reference image
python3 ~/.claude/skills/nanobanana/generate_openai.py "Change background to night sky" \
  -r "/tmp/reference_image.png" -o edited.png

Legacy Method (When Path is in Metadata)

If image metadata contains [Image: source: /path/to/image.png], use that path directly.

python3 ~/.claude/skills/nanobanana/generate.py "Same style. Object: cat" \
  -r "/Users/user/Desktop/reference.png" -o cat.png

Note: Always wrap paths containing spaces in double quotes.

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Pre-generation Confirmation Flow

Important: Before starting image generation, always confirm the following using the AskUserQuestion tool.

Confirmation Items

Common (Always Confirm):

Item	Options	Description
Provider	gemini / openai	gemini=Nano Banana, openai=GPT Image
Model	Gemini: pro/flash, OpenAI: 1.5/1/mini	See details below
Reference Image	Yes / No	Whether there's a source image to copy style from (pasted images can be used)
Background Removal	Vision API / Magenta removal / OpenAI transparent / Not needed	See methods below

Additional for Multiple Image Generation:

Item	Options	Description
Generation Method	Sheet→split / Parallel generation	Sheet→split recommended (efficient)

Provider Characteristics

Provider	Strengths	API Key Environment Variable
Gemini	Japanese prompts, reference image style copying	GEMINI_API_KEY
OpenAI	High quality, native transparent background, multiple simultaneous generation	OPENAI_API_KEY

Model Comparison

Gemini:

Model	ID	Features
Flash	gemini-2.5-flash-image	Fast, cost-efficient
Pro	gemini-3-pro-image-preview	High quality, handles complex instructions

OpenAI:

Model	ID	Features
GPT Image 1.5	gpt-image-1.5	Latest & highest quality (recommended)
GPT Image 1	gpt-image-1	Standard model
GPT Image Mini	gpt-image-1-mini	Lightweight, fast, low cost

Background Removal Method Selection

Method	Best For	Provider
OpenAI Transparent	Use --background transparent for direct transparent generation with OpenAI	OpenAI only
Vision API	Real photos, photo-style, complex backgrounds, gradient backgrounds	Gemini
Magenta Removal	Illustrations, simple shapes, line art, flat design	Gemini

Recommended Settings

Case	Provider	Model	Background Removal
Transparent icons/stickers	OpenAI	1.5	--background transparent
Reference image style copy	Gemini	pro	Vision API
Simple illustrations	Gemini	flash	Magenta removal
High quality illustrations	OpenAI	1.5	None or transparent
Prototype/testing	OpenAI	mini	None

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Tool List

Tool	Description
generate.py	Gemini image generation
generate_openai.py	OpenAI image generation
remove-bg-magenta.py	Magenta background removal (includes 1px erosion)
remove-bg-vision.py	Vision API background removal
erode.py	Transparent image edge erosion
split_transparent.py	Split transparent image into individual objects

Prerequisites

1. For Gemini: Set environment variable GEMINI_API_KEY
2. For OpenAI: Set environment variable OPENAI_API_KEY
3. Vision API: Requires macOS 14.0 (Sonoma) or later

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1. generate.py - Gemini Image Generation

python3 ~/.claude/skills/nanobanana/generate.py "prompt" [options]

Options

Option	Description	Default
-o, --output	Output file path	generated_image.png
-a, --aspect-ratio	Aspect ratio (1:1, 16:9, 9:16, 4:3, 3:4)	1:1
-m, --model	Model (flash, pro)	pro
--magenta-bg	Generate with magenta background	None
-r, --reference	Reference image path	None

Examples

# Simple generation
python3 ~/.claude/skills/nanobanana/generate.py "cute cat illustration"

# Copy reference image style
python3 ~/.claude/skills/nanobanana/generate.py "Same exact style as this image. Object: coffee cup. NO text." -r reference.png -o coffee.png

# Generate with magenta background (for later transparency processing)
python3 ~/.claude/skills/nanobanana/generate.py "simple star icon" --magenta-bg -o star.png

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2. generate_openai.py - OpenAI Image Generation

python3 ~/.claude/skills/nanobanana/generate_openai.py "prompt" [options]

Options

Option	Description	Default
-o, --output	Output file path	generated_image.png
-s, --size	Size (1024x1024, 1536x1024, 1024x1536, auto)	1024x1024
-m, --model	Model (gpt-image-1, gpt-image-1-mini, gpt-image-1.5)	gpt-image-1.5
-q, --quality	Quality (low, medium, high)	medium
-b, --background	Background (transparent, opaque, auto)	auto
-f, --format	Output format (png, jpeg, webp)	png
-r, --reference	Image path to edit	None
-n, --number	Number of images to generate (1-10)	1

Examples

# Simple generation
python3 ~/.claude/skills/nanobanana/generate_openai.py "cute cat illustration"

# Generate with transparent background (no background removal needed)
python3 ~/.claude/skills/nanobanana/generate_openai.py "simple star icon" -b transparent -o star.png

# High quality, landscape
python3 ~/.claude/skills/nanobanana/generate_openai.py "sunset landscape" -s 1536x1024 -q high -o sunset.png

# Generate multiple simultaneously
python3 ~/.claude/skills/nanobanana/generate_openai.py "cute animal icon, single animal" -n 5 -b transparent -o animals.png

# Image editing
python3 ~/.claude/skills/nanobanana/generate_openai.py "change background to night sky" -r input.png -o edited.png

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3. remove-bg-magenta.py - Magenta Background Removal

Remove magenta/pink background using color-based detection.

python3 ~/.claude/skills/nanobanana/remove-bg-magenta.py input_image [-o output_image]

How it Works

• Makes colors with R>180, G<100, B>100 transparent
• 1px erosion removes pink edge residue

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4. remove-bg-vision.py - Vision API Background Removal

Automatically detect and remove background using macOS Vision API.

python3 ~/.claude/skills/nanobanana/remove-bg-vision.py input_image [-o output_image]

Features

• Automatic foreground detection
• Best for images maintaining reference image style (including background)
• Requires macOS 14.0 or later

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5. erode.py - Edge Erosion

Erode transparent image edges by specified pixels.

python3 ~/.claude/skills/nanobanana/erode.py input_image [-o output_image] [-i iterations]

Option	Description	Default
-o, --output	Output image path	Overwrites input
-i, --iterations	Erosion amount (pixels)	1

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6. split_transparent.py - Transparent Image Splitting

Split transparent PNG into individual objects (for sticker sheets).

python3 ~/.claude/skills/nanobanana/split_transparent.py input_image [output_directory]

How it Works

• Detects boundaries using alpha channel (transparent areas)
• Extracts each connected component
• Numbers from top-left to bottom-right

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Workflow Examples

Generate Using Pasted Image as Reference (Recommended)

When user pastes an image, copy from image-cache to tmp and use as reference.

# 1. Check image-cache path from Additional working directories in environment info
# Example: /Users/username/.claude/image-cache/0353f5a1-9885-4743-a956-d2d195b445d4

# 2. Copy from image-cache to tmp
cp ~/.claude/image-cache/0353f5a1-9885-4743-a956-d2d195b445d4/*.png /tmp/reference_image.png

# 3. Gemini: Generate different object in same style
python3 ~/.claude/skills/nanobanana/generate.py "Same exact style as this image. Object: coffee cup. NO text." \
  -r "/tmp/reference_image.png" -o coffee.png

# 4. OpenAI: Edit image
python3 ~/.claude/skills/nanobanana/generate_openai.py "change background to outer space" \
  -r "/tmp/reference_image.png" -o space.png

OpenAI: Transparent Icon Generation (Recommended - Simplest)

# Generate transparent PNG in one step
python3 ~/.claude/skills/nanobanana/generate_openai.py "simple star icon" -b transparent -o star.png

OpenAI: Multiple Icon Simultaneous Generation

# Generate 5 transparent PNGs simultaneously
python3 ~/.claude/skills/nanobanana/generate_openai.py "cute animal icon, single animal" -n 5 -b transparent -o animal.png
# → animal_01.png, animal_02.png, ... will be generated

Gemini: Transparent Sticker Generation (Simple Objects)

# 1. Generate with magenta background
python3 ~/.claude/skills/nanobanana/generate.py "simple star icon" --magenta-bg -o star.png

# 2. Remove magenta
python3 ~/.claude/skills/nanobanana/remove-bg-magenta.py star.png

Gemini: Reference Image Style Copy + Transparency

# 1. Generate with reference image style (no magenta to maintain style)
python3 ~/.claude/skills/nanobanana/generate.py "Same exact style as this image. Object: coffee cup. NO text." -r reference.png -o coffee.png

# 2. Remove background with Vision API
python3 ~/.claude/skills/nanobanana/remove-bg-vision.py coffee.png

Gemini: Sticker Sheet Generation → Split

# 1. Generate multiple stickers with magenta background
python3 ~/.claude/skills/nanobanana/generate.py \
  "Multiple separate kawaii stickers with LARGE gaps: coffee cup, donut, cat, star. Arranged in 2x2 grid, well separated." \
  --magenta-bg -o sheet.png

# 2. Make background transparent
python3 ~/.claude/skills/nanobanana/remove-bg-magenta.py sheet.png

# 3. Split into individual files
python3 ~/.claude/skills/nanobanana/split_transparent.py sheet.png ./stickers/

Prompt Tips:

• LARGE gaps between them - Wide spacing
• well separated - No overlapping
• Arranged in XxY grid - Specify grid layout

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File Structure

~/.claude/skills/nanobanana/
├── SKILL.md               # This document
├── generate.py            # Gemini image generation
├── generate_openai.py     # OpenAI image generation
├── remove-bg-magenta.py   # Magenta background removal (includes 1px erosion)
├── remove-bg-vision.py    # Vision API background removal
├── remove-bg.swift        # Vision API implementation (Swift)
├── erode.py               # Edge erosion (standalone)
└── split_transparent.py   # Transparent image splitting