Agent skill

nano-banana-2

Generate and edit images using Google's Nano Banana 2 (Gemini 3.1 Flash Image Preview) API. This skill should be used when the user asks to create or modify images, especially when they need fast iteration, explicit aspect-ratio control, or resolution control from 512px to 4K.

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Install this agent skill to your Project

npx add-skill https://github.com/intellectronica/agent-skills/tree/main/skills/nano-banana-2

SKILL.md

Nano Banana 2 Image Generation & Editing

Generate new images or edit existing images with Nano Banana 2 (gemini-3.1-flash-image-preview).

Usage

Run the script using absolute or workspace-relative path (do NOT cd into the skill directory first):

Generate new image:

bash
uv run ./.agents/skills/nano-banana-2/scripts/generate_image.py --prompt "your image description" --filename "output-name.png" [--resolution 512px|1K|2K|4K] [--aspect-ratio RATIO] [--api-key KEY]

Edit image(s) with references:

bash
uv run ./.agents/skills/nano-banana-2/scripts/generate_image.py --prompt "editing instructions" --filename "output-name.png" --input-image "path/to/input1.png" [--input-image "path/to/input2.png" ...] [--resolution 512px|1K|2K|4K] [--aspect-ratio RATIO] [--api-key KEY]

Always run from the user's current working directory so outputs are saved in the active project context.

Model

Use model code:

  • gemini-3.1-flash-image-preview (Nano Banana 2)

Do not use gemini-3-pro-image-preview in this skill.

Resolution Options

Nano Banana 2 supports:

  • 512px (fastest, low-latency iteration)
  • 1K (default)
  • 2K
  • 4K

Map common user language:

  • "quick draft", "thumbnail", "tiny", "512", "0.5K" → 512px
  • no resolution mention → 1K
  • "2K", "medium", "normal" → 2K
  • "4K", "high-res", "ultra", "print quality" → 4K

Use uppercase K for 1K, 2K, 4K.

Aspect Ratios

Supported aspect ratios:

  • 1:1, 1:4, 1:8, 2:3, 3:2, 3:4, 4:1, 4:3, 4:5, 5:4, 8:1, 9:16, 16:9, 21:9

Map common requests:

  • square post / icon → 1:1
  • phone wallpaper / vertical reel → 9:16
  • widescreen / slide / hero image → 16:9
  • cinematic wide → 21:9
  • portrait print → 2:3 or 3:4
  • panorama banner → 4:1 or 8:1

If unspecified, let the model default behavior apply.

Reference Images (New in Gemini 3 Image workflows)

Provide up to 14 reference images when needed by repeating --input-image:

  • preserve character consistency
  • preserve object fidelity
  • combine multiple visual references into one output

Use one image for simple edits; use multiple images for composition or consistency-sensitive tasks.

API Key

Resolve API key in this order:

  1. --api-key argument
  2. GEMINI_API_KEY environment variable

If no key is available, stop and report a clear error.

Filename Generation

Generate filenames as: yyyy-mm-dd-hh-mm-ss-name.png

Examples:

  • 2026-02-26-17-31-04-japanese-garden.png
  • 2026-02-26-17-31-59-social-banner.png

Prompt Handling

For generation, pass the user's request as-is unless critically underspecified. For editing, include explicit transformation instructions in the prompt and preserve the original intent.

Output

  • Save PNG to the current directory (or to a provided path in --filename)
  • Return the full saved path(s)
  • Do not read the output image back unless explicitly requested

Examples

Create a 4K widescreen image:

bash
uv run ./.agents/skills/nano-banana-2/scripts/generate_image.py --prompt "Futuristic city skyline at blue hour with neon reflections" --filename "2026-02-26-17-45-00-futuristic-skyline.png" --resolution 4K --aspect-ratio 16:9

Edit with multiple references:

bash
uv run ./.agents/skills/nano-banana-2/scripts/generate_image.py --prompt "Create a polished campaign image that keeps the exact logo details and character identity" --filename "2026-02-26-17-50-10-campaign-image.png" --input-image "logo.png" --input-image "character.png" --resolution 2K --aspect-ratio 4:5

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