Nano Banana - Gemini Image Generation
Generate and edit images from text prompts via Google's Gemini image generation API.
When to Use
- User requests image generation, creation, or production from a text description
- Editing existing images with text instructions
- Style-transfer: generate new images that match the aesthetic of a reference
- Creating illustrations for presentations, articles, thumbnails, social posts
- Batch variations of the same concept
First-Time Setup
scripts/nano_banana.py initWizard checks dependencies (sops, age, magick), verifies the API key, and saves defaults to ~/.config/nano-banana/config.yaml.
Quick Start
# Simple generation
scripts/nano_banana.py "a minimalist illustration of a rocket" ./rocket.png
# With style preset
scripts/nano_banana.py --preset editorial "interconnected nodes" ./nodes.png
# YouTube thumbnail (auto-cropped to 1280x720)
scripts/nano_banana.py --preset grain --platform youtube "coffee on desk" ./thumb.png
# Generate 4 variants + contact sheet
scripts/nano_banana.py --preset wireframe "a crystal" ./crystal.png --n 4
# Edit existing image
scripts/nano_banana.py --edit ./old.png "make the background deep teal" ./new.png
# Style reference (match aesthetic of existing image)
scripts/nano_banana.py --reference ./style.png "a new mountain landscape" ./mountain.png
# Re-roll last prompt
scripts/nano_banana.py again
# View history
scripts/nano_banana.py history -n 10Requirements
GEMINI_API_KEY— auto-decrypted fromsecrets.enc.yamlvia SOPS + age. Fallback:export GEMINI_API_KEY=...sops,age— for key decryptionmagick(ImageMagick) — for platform fit + contact sheetspython3withpyyaml
Models
| Model | Alias | Nano Banana Name | Use When |
|---|---|---|---|
gemini-3.1-flash-image-preview (default) | flash | Nano Banana 2 | Best instruction following, fast |
gemini-3-pro-image-preview | pro | Nano Banana Pro | Highest quality, text in images |
gemini-2.5-flash-image | flash-2.5 | Nano Banana (original) | Legacy |
Use via --model flash|pro|flash-2.5 or full ID.
Style Presets
scripts/nano_banana.py list-presets
scripts/nano_banana.py --preset editorial "your subject" out.png| Preset | Style |
|---|---|
editorial | Thin lines on black, muted palette, technical diagram feel |
blueprint | White/cyan lines on dark navy, engineering drawing |
ink | Japanese sumi-e ink wash, organic brushstrokes, monochrome |
risograph | Flat colors, grain, terracotta + sage, zine aesthetic |
wireframe | 3D wireframe mesh, glowing edges on black |
constellation | Star map dots connected by faint lines, celestial |
brutalist | Bold shapes, thick borders, hard shadows, flat colors |
grain | Film grain photo, high ISO, warm cinematic tones |
Defined in presets.yaml — edit to add your own.
Platform Presets
scripts/nano_banana.py list-platforms
scripts/nano_banana.py --platform youtube "your subject" out.pngGenerated image is automatically resized + center-cropped to target dimensions.
| Platform | Size |
|---|---|
youtube | 1280×720 |
youtube-short | 1080×1920 |
slides | 1920×1080 |
blog | 1200×630 |
x | 1600×900 |
square | 1080×1080 |
story | 1080×1920 |
pinterest | 1000×1500 |
Features
Variants + Contact Sheet
--n N generates N variants in parallel and assembles them into a contact sheet:
scripts/nano_banana.py --preset ink "mountain" ./mt.png --n 6
# Creates mt-01.png ... mt-06.png + mt-contact.pngEdit Mode
Pass an existing image and the prompt becomes the edit instruction:
scripts/nano_banana.py --edit ./thumb.png "remove the watermark, warmer colors" ./clean.pngReference Images (Style Anchor)
Use one or more reference images to guide the aesthetic without editing them:
scripts/nano_banana.py --reference ./episode1.png --reference ./episode2.png \
"episode 3: data drift" ./ep3.pngProjects + Metadata
Organize outputs by project:
scripts/nano_banana.py --project lab-04/meeting-02 --preset editorial "MCP loops" ./overlay.png
# Saves to ~/nano-banana/outputs/lab-04/meeting-02/20260414-<subject>.png + .json sidecarRe-roll + History
scripts/nano_banana.py again # rerun last prompt
scripts/nano_banana.py history -n 20 # show last 20 generations
scripts/nano_banana.py history --project lab-04Dry Run
Preview the composed prompt without calling the API:
scripts/nano_banana.py --preset editorial --platform youtube "subject" --dry-runTransient Errors & Retry
The API occasionally returns 500/INTERNAL or empty candidates. The script retries up to 4 times with exponential backoff (2s, 4s, 8s, 16s). Permanent errors (4xx, safety violations) fail fast without retry.
Prompt Tips
- Specify visual style: "photograph", "flat illustration", "watercolor", "3D render"
- Include composition: "centered", "white background", "wide shot"
- Name colors: "blue and white color scheme", "warm earth tones"
- For text rendering, use
--model proand quote exact text:'with the text "Hello"'
See references/api_reference.md for full API documentation.
Files
scripts/nano_banana.py— main CLI (Python)scripts/generate_image.sh— thin bash wrapper (back-compat)presets.yaml— style presetsplatforms.yaml— platform sizing presetssecrets.enc.yaml— encrypted API key (SOPS + age)~/.config/nano-banana/config.yaml— user defaults (frominit)~/.config/nano-banana/history.jsonl— generation log~/.config/nano-banana/last.json— last run (foragain)