/nano-banana-2

name: nano-banana-2
description: 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.

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:**

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:**

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:**

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:**

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