Nano Banana - Gemini Image Generation Skill

Nano Banana - Gemini Image Generation

This skill provides comprehensive access to Gemini's image generation capabilities, including text-to-image generation, image editing, multi-turn refinement, batch processing, and high-resolution output.

Prerequisites

API key set as GOOGLE_API_KEY or GEMINI_API_KEY environment variable
The scripts include a bundled virtual environment (.venv/) with google-genai pre-installed
Scripts can be called directly: ~/.claude/skills/nano-banana/scripts/generate_image.py

Available Models

| Model | ID | Best For | |-------|----|----------| | Flash | gemini-2.5-flash-image | Fast generation, high volume, low latency | | Pro | gemini-3-pro-image-preview | Professional quality, 4K, advanced reasoning |

Capabilities Overview

| Capability | Script | Description | |------------|--------|-------------| | Image Generation | generate_image.py | Create images from text prompts | | Image Editing | edit_image.py | Modify existing images with instructions | | Batch Generation | batch_generate.py | Generate multiple images in parallel | | Multi-turn Editing | chat_session.py | Iterative refinement via conversation |

Quick Start

Generate a Single Image

python scripts/generate_image.py "a sunset over mountains" sunset.png

With options:

python scripts/generate_image.py "modern office" office.png --model pro --aspect 16:9 --size 4K

Edit an Existing Image

python scripts/edit_image.py photo.png "remove the background" result.png

Batch Generation

Create a prompts file (prompts.json):

[
    {"prompt": "slide 1: intro graphic", "filename": "slide_01.png", "aspect": "16:9"},
    {"prompt": "slide 2: data visualization", "filename": "slide_02.png", "aspect": "16:9"}
]

Generate all:

python scripts/batch_generate.py prompts.json ./output/ --parallel 3

Or use a simple text file (one prompt per line):

python scripts/batch_generate.py prompts.txt ./output/ --aspect 16:9

Multi-turn Editing Session

Start an interactive session:

python scripts/chat_session.py --output-dir ./images/

Resume a previous session:

python scripts/chat_session.py --session-file session.json

Send a single refinement:

python scripts/chat_session.py --session-file session.json --message "make it more vibrant"

Script Reference

generate_image.py

Generate a single image from a text prompt.

Usage: python scripts/generate_image.py "prompt" output.png [options]

Options:
  --model, -m    Model: flash (default) or pro
  --aspect, -a   Aspect ratio: 1:1 (default), 16:9, 9:16, 21:9, 4:3, 3:4
  --size, -s     Resolution (pro only): 1K, 2K, 4K

edit_image.py

Edit an existing image using text instructions.

Usage: python scripts/edit_image.py input.png "instructions" output.png [options]

Options:
  --model, -m    Model: flash (default) or pro

batch_generate.py

Generate multiple images from a prompts file.

Usage: python scripts/batch_generate.py prompts.json output_dir/ [options]

Options:
  --model, -m     Model: flash (default) or pro
  --aspect, -a    Default aspect ratio: 1:1 (default)
  --parallel, -p  Number of parallel workers: 1 (default)
  --json          Output results as JSON

chat_session.py

Multi-turn image generation/editing session.

Usage: python scripts/chat_session.py [options]

Options:
  --model, -m        Model: flash (default) or pro
  --session-file, -s Path to session state file (JSON)
  --output-dir, -o   Directory for output images: . (default)
  --initial, -i      Initial prompt to start with
  --message          Send single message (non-interactive)

Best Practices

Prompting Tips

Be specific: "A red sports car on a mountain road at sunset" works better than "a car".
Describe style: Include art style, mood, lighting, and camera angle.
Use negative space: Describe what should NOT be in the image when needed.

Editing Tips

Target specific elements: "Change only the sky to purple" is better than "make it purple".
Reference the original: "Keep the composition but change the color scheme".
Iterative refinement: Use multi-turn sessions for complex edits.

Performance

Use flash model for quick iterations and high volume.
Use pro model for final production assets and 4K output.
Use batch generation with --parallel for multiple images.

Additional Resources

For detailed API documentation, see references/gemini-api.md. For prompting techniques, see references/prompt-guide.md. For common editing patterns, see references/editing-patterns.md.

Agent Skills: Nano Banana - Gemini Image Generation

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