ReScienceLab/nanobanana

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

1. Generate 10-20 variations to explore options
2. Use consistent prompts for style coherence
3. Add 3-5 second delays to avoid rate limits
4. 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