Nano Banana Image Generation
Generate and edit images via the Gemini Nano Banana API using Python or JavaScript scripts.
Setup
Before generating images, verify the API key exists:
bash
[ -n "$GEMINI_API_KEY" ] && echo "API key configured" || echo "Missing GEMINI_API_KEY"
Install dependencies based on the user's environment:
bash
# Python pip install google-genai Pillow # JavaScript npm install @google/genai
Script Usage
Python
bash
python scripts/generate_image.py "prompt" [options]
JavaScript
bash
node scripts/generate_image.mjs "prompt" [options]
Options
| Option | Description |
|---|---|
-o, --output | Output filename (default: generated_image.png) |
-m, --model | flash (fast, default) or pro (high-quality, 4K) |
-a, --aspect | Aspect ratio: 1:1, 16:9, 9:16, 2:3, 3:2, etc. |
-s, --size | Resolution for pro model: 1K, 2K, 4K |
-e, --edit | Input image path for editing |
--search | Enable Google Search grounding (pro only) |
Generation Examples
Text to Image
bash
# Blog header python scripts/generate_image.py "modern flat illustration of developer coding, purple gradient background, minimalist style, no text" -a 16:9 -o header.png # YouTube thumbnail python scripts/generate_image.py "professional editorial photo of coffee on wooden desk, morning sunlight, shallow depth of field" -a 16:9 -o thumbnail.png # Logo python scripts/generate_image.py "minimalist logo for coffee shop called 'The Daily Grind', clean sans-serif font, black and white, coffee bean motif" -m pro -a 1:1 -o logo.png # Icon python scripts/generate_image.py "kawaii-style app icon of a happy robot, bold outlines, vibrant colors, white background" -a 1:1 -o icon.png
Image Editing
bash
# Add element python scripts/generate_image.py "Add a small wizard hat on the cat's head, matching the soft lighting" -e cat.jpg -o cat_wizard.png # Style transfer python scripts/generate_image.py "Transform into Van Gogh's Starry Night style with swirling brushstrokes" -e city.png -o city_art.png # Modify element python scripts/generate_image.py "Change the blue sofa to a brown leather chesterfield, keep everything else unchanged" -e room.jpg -o room_edited.png
Real-Time Content (Pro Model)
bash
# Weather visualization python scripts/generate_image.py "Current 5-day weather forecast for San Francisco as a modern chart" -m pro --search -a 16:9 -o weather.png # Sports graphic python scripts/generate_image.py "Stylish graphic of last night's game score" -m pro --search -o score.png
Model Selection
| Model | Use Case | Resolution | Cost |
|---|---|---|---|
| flash | Fast generation, high volume | 1024px | ~$0.04/image |
| pro | Professional assets, text rendering, 4K | Up to 4K | Higher |
Use pro for:
- •Accurate text in images (logos, infographics)
- •High-resolution output (2K, 4K)
- •Real-time data with Google Search
- •Complex multi-turn editing
Use flash for:
- •Quick iterations
- •High-volume generation
- •Standard resolution needs
Aspect Ratios
| Use Case | Ratio | Example |
|---|---|---|
| YouTube thumbnail | 16:9 | 1344x768 |
| Blog featured image | 16:9 | 1344x768 |
| Instagram square | 1:1 | 1024x1024 |
| Story/Reels | 9:16 | 768x1344 |
| Twitter header | 21:9 | 1536x672 |
| Portrait | 2:3 | 832x1248 |
Prompt Guidelines
Write descriptive scenes, not keyword lists:
Effective: "A photorealistic close-up portrait of a ceramicist with sun-etched wrinkles, inspecting a glazed tea bowl in a sunlit workshop. Soft golden hour light from a window, 85mm lens with bokeh."
Weak: "old man, pottery, workshop, golden hour"
Tips
- •Describe the scene narratively
- •Specify style: "editorial photography", "flat illustration", "watercolor"
- •Include lighting, camera angle, mood
- •Add "no text" if unwanted text appears
- •Use "white background" or "transparent background" for assets
Limitations
- •Supported languages: EN, ar-EG, de-DE, es-MX, fr-FR, hi-IN, id-ID, it-IT, ja-JP, ko-KR, pt-BR, ru-RU, ua-UA, vi-VN, zh-CN
- •No audio or video inputs
- •flash: up to 3 input images; pro: up to 14 input images
- •Output count may vary from request
- •All images include SynthID watermark
Troubleshooting
| Problem | Solution |
|---|---|
| Missing API key | Set GEMINI_API_KEY environment variable |
| Package not found | Run pip/npm install commands |
| No image generated | Simplify prompt, check for policy violations |
| Poor text rendering | Use pro model for text-heavy images |
| Wrong aspect ratio | Explicitly set -a option |
Reference
For complete API documentation, prompting strategies, and code examples in multiple languages, see references/nano-banana-docs.md.