nanobanana

SKILL.md

Nano Banana - AI Image Generation

Generate and edit images using Google's Gemini 3 Pro Image model (gemini-3-pro-image-preview, nicknamed "Nano Banana Pro" 🍌).

Prerequisites

Required:

GEMINI_API_KEY - Get from Google AI Studio

Python 3.10+ with google-genai package

Install dependencies:

pip install google-genai pillow

Quick Start
Generate an image:

python3 <skill_dir>/scripts/generate.py "a cute robot mascot, pixel art style" -o robot.png

Edit an existing image:

python3 <skill_dir>/scripts/generate.py "make the background blue" -i input.jpg -o output.png

Generate with specific aspect ratio:

python3 <skill_dir>/scripts/generate.py "cinematic landscape" --ratio 21:9 -o landscape.png

Generate high-resolution 4K image:

python3 <skill_dir>/scripts/generate.py "professional product photo" --size 4K -o product.png

Script Reference

scripts/generate.py

Main image generation script.

Usage: generate.py [OPTIONS] PROMPT

Arguments:
  PROMPT              Text prompt for image generation

Options:
  -o, --output PATH   Output file path (default: auto-generated)
  -i, --input PATH    Input image for editing (optional)
  -r, --ratio RATIO   Aspect ratio (1:1, 16:9, 9:16, 21:9, etc.)
  -s, --size SIZE     Image size: 2K or 4K (default: standard)
  --search            Enable Google Search grounding for accuracy
  -v, --verbose       Show detailed output

Supported aspect ratios:

1:1 - Square (default)

2:3, 3:2 - Portrait/Landscape

3:4, 4:3 - Standard

4:5, 5:4 - Photo

9:16, 16:9 - Widescreen

21:9 - Ultra-wide/Cinematic

scripts/batch_generate.py

Generate multiple images with sequential naming.

Usage: batch_generate.py [OPTIONS] PROMPT

Arguments:
  PROMPT              Text prompt for image generation

Options:
  -n, --count N       Number of images to generate (default: 10)
  -d, --dir PATH      Output directory
  -p, --prefix STR    Filename prefix (default: "image")
  -r, --ratio RATIO   Aspect ratio
  -s, --size SIZE     Image size (2K/4K)
  --delay SECONDS     Delay between generations (default: 3)

Example:

python3 <skill_dir>/scripts/batch_generate.py "pixel art logo" -n 20 -d ./logos -p logo

Python API

You can also use the module directly:

from generate import generate_image, edit_image

# Generate image
result = generate_image(
    prompt="a futuristic city at night",
    output_path="city.png",
    aspect_ratio="16:9",
    image_size="4K"
)

# Edit existing image
result = edit_image(
    prompt="add flying cars to the sky",
    input_path="city.png",
    output_path="city_edited.png"
)

Environment Variables

Variable
Description
Default

GEMINI_API_KEY
Google Gemini API key
Required

IMAGE_OUTPUT_DIR
Default output directory
./nanobanana-images

Features

Text-to-Image Generation

Create images from text descriptions. The model excels at:

Photorealistic images

Artistic styles (pixel art, illustration, etc.)

Product photography

Landscapes and scenes

Image Editing

Transform existing images with natural language:

Style transfer

Object addition/removal

Background changes

Color adjustments

High-Resolution Output

Standard: Fast generation, good quality

2K: Enhanced detail (2048px)

4K: Maximum quality (3840px), best for text rendering

Google Search Grounding

Enable --search for factually accurate images involving:

Real people, places, landmarks

Current events

Specific products or brands

Best Practices

Prompt Writing

Good prompts include:

Subject description

Style/aesthetic

Lighting and mood

Composition details

Color palette

Example:

"A cozy coffee shop interior, warm lighting, vintage aesthetic, 
wooden furniture, plants on shelves, morning sunlight through windows, 
soft focus background, 35mm film photography style"

Batch Generation Tips

Generate 10-20 variations to explore options

Use consistent prompts for style coherence

Add 3-5 second delays to avoid rate limits

Review results and iterate on best candidates

Rate Limits

Gemini API has usage quotas

Add delays between batch generations

Check your quota at Google AI Studio

Troubleshooting

"API key not found"

Set GEMINI_API_KEY environment variable

Or pass via --api-key option

"No image in response"

Prompt may have triggered safety filters

Try rephrasing to avoid sensitive content

"Rate limit exceeded"

Wait a few seconds and retry

Reduce batch size or add longer delays

References

references/prompts.md - Prompt examples by category

examples/ - Example usage scripts