nano-banana

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Generate and edit images using Google's Gemini image generation models (Nano Banana family). Supports style presets, platform-specific sizing (YouTube/slides/blog), variants, image editing via inlineData, reference images for style transfer, and organized output with metadata. Default model is Nano Banana 2 (gemini-3.1-flash-image-preview). Key is auto-decrypted via SOPS.

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NPX Install

npx skill4agent add glebis/claude-skills nano-banana

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gemini-image-generationnano-bananaimage-editingstyle-transfercli-tool

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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

bash
scripts/nano_banana.py init
Wizard checks dependencies (sops, age, magick), verifies the API key, and saves defaults to 
~/.config/nano-banana/config.yaml
.

Quick Start

bash
# 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 10

Requirements

  • GEMINI_API_KEY
    — auto-decrypted from 
    secrets.enc.yaml
    via SOPS + age. Fallback: 
    export GEMINI_API_KEY=...
  • sops
    , 
    age
    — for key decryption
  • magick
    (ImageMagick) — for platform fit + contact sheets
  • python3
    with 
    pyyaml

Models

ModelAliasNano Banana NameUse When
gemini-3.1-flash-image-preview
(default)
flash
Nano Banana 2Best instruction following, fast
gemini-3-pro-image-preview
pro
Nano Banana ProHighest 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

bash
scripts/nano_banana.py list-presets
scripts/nano_banana.py --preset editorial "your subject" out.png
PresetStyle
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

bash
scripts/nano_banana.py list-platforms
scripts/nano_banana.py --platform youtube "your subject" out.png
Generated image is automatically resized + center-cropped to target dimensions.
PlatformSize
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:
bash
scripts/nano_banana.py --preset ink "mountain" ./mt.png --n 6
# Creates mt-01.png ... mt-06.png + mt-contact.png

Edit Mode

Pass an existing image and the prompt becomes the edit instruction:
bash
scripts/nano_banana.py --edit ./thumb.png "remove the watermark, warmer colors" ./clean.png

Reference Images (Style Anchor)

Use one or more reference images to guide the aesthetic without editing them:
bash
scripts/nano_banana.py --reference ./episode1.png --reference ./episode2.png \
  "episode 3: data drift" ./ep3.png

Projects + Metadata

Organize outputs by project:
bash
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 sidecar

Re-roll + History

bash
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-04

Dry Run

Preview the composed prompt without calling the API:
bash
scripts/nano_banana.py --preset editorial --platform youtube "subject" --dry-run

Transient 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 pro
    and 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 presets
  • platforms.yaml
    — platform sizing presets
  • secrets.enc.yaml
    — encrypted API key (SOPS + age)
  • ~/.config/nano-banana/config.yaml
    — user defaults (from 
    init
    )
  • ~/.config/nano-banana/history.jsonl
    — generation log
  • ~/.config/nano-banana/last.json
    — last run (for 
    again
    )