Nano Banana Pro

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name: nano-banana-pro description: Use Nano Banana 2 (Gemini 3.1 Flash Image), the newest image model focused on faster iteration, lower cost, and strong quality. Published 2026-02-26 as the latest Flash-image generation family update. Supports image generation/edit, image-to-image, and 1K/2K/4K.

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Nano Banana 2 (Gemini 3.1 Flash Image) - Faster, lower-cost image generation & editing

Generate new images or edit existing ones using Nano Banana 2 (gemini-3.1-flash-image-preview), Google’s newer image family that targets faster iterative generation and stronger price/performance balance while staying in the same image-editing workflow.

Why Nano Banana 2 (Gemini 3.1 Flash Image)

Newer release path: Gemini 3.1 Flash Image is documented as the 26 Feb 2026 Flash-image family release (vs. Nano Banana Pro’s 20 Nov 2025 release date for image preview).

Faster iteration: Google docs position Gemini 3.1 Flash Image as optimized for image understanding/generation with a balance of price and performance.

Cost focus: It is marketed for lower-cost, faster iterative image generation workflows compared with older Pro-first quality-first defaults.

Strong baseline quality: It remains suitable for professional generation/editing and supports multi-image editing/multi-turn workflows in the same API flow.

Use this as the default for drafts and quick turns; use higher-cost variants when you need a specific quality edge on a non-time-critical final pass.

Usage

Run the script using absolute path (do NOT cd to skill directory first):

Generate new image:

uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "your image description" --filename "output-name.png" [--resolution 1K|2K|4K] [--api-key KEY]

Edit existing image:

uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "editing instructions" --filename "output-name.png" --input-image "path/to/input.png" [--resolution 1K|2K|4K] [--api-key KEY]

Important: Always run from the user's current working directory so images are saved where the user is working, not in the skill directory.

Default Workflow (draft → iterate → final)

Goal: fast iteration without burning time on 4K until the prompt is correct.

Draft (1K): quick feedback loop

- uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "" --filename "yyyy-mm-dd-hh-mm-ss-draft.png" --resolution 1K

Iterate: adjust prompt in small diffs; keep filename new per run

- If editing: keep the same --input-image for every iteration until you’re happy.

Final (4K): only when prompt is locked

- uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "" --filename "yyyy-mm-dd-hh-mm-ss-final.png" --resolution 4K

Resolution Options

The Nano Banana 2 / Gemini 3.1 Flash Image API supports three resolutions (uppercase K required):

1K (default) - ~1024px resolution

2K - ~2048px resolution

4K - ~4096px resolution

Map user requests to API parameters:

No mention of resolution → 1K

"low resolution", "1080", "1080p", "1K" → 1K

"2K", "2048", "normal", "medium resolution" → 2K

"high resolution", "high-res", "hi-res", "4K", "ultra" → 4K

API Key

The script checks for API key in this order: 1. --api-key argument (use if user provided key in chat) 2. GEMINI_API_KEY environment variable

If neither is available, the script exits with an error message.

Preflight + Common Failures (fast fixes)

Preflight:

- command -v uv (must exist) - test -n \"$GEMINI_API_KEY\" (or pass --api-key) - If editing: test -f \"path/to/input.png\"

Common failures:

- Error: No API key provided. → set GEMINI_API_KEY or pass --api-key - Error loading input image: → wrong path / unreadable file; verify --input-image points to a real image - “quota/permission/403” style API errors → wrong key, no access, or quota exceeded; try a different key/account

Filename Generation

Generate filenames with the pattern: yyyy-mm-dd-hh-mm-ss-name.png

Format: {timestamp}-{descriptive-name}.png

Timestamp: Current date/time in format yyyy-mm-dd-hh-mm-ss (24-hour format)

Name: Descriptive lowercase text with hyphens

Keep the descriptive part concise (1-5 words typically)

Use context from user's prompt or conversation

If unclear, use random identifier (e.g., x9k2, a7b3)

Examples:

Prompt "A serene Japanese garden" → 2025-11-23-14-23-05-japanese-garden.png

Prompt "sunset over mountains" → 2025-11-23-15-30-12-sunset-mountains.png

Prompt "create an image of a robot" → 2025-11-23-16-45-33-robot.png

Unclear context → 2025-11-23-17-12-48-x9k2.png

Image Editing

When the user wants to modify an existing image: 1. Check if they provide an image path or reference an image in the current directory 2. Use --input-image parameter with the path to the image 3. The prompt should contain editing instructions (e.g., "make the sky more dramatic", "remove the person", "change to cartoon style") 4. Common editing tasks: add/remove elements, change style, adjust colors, blur background, etc.

Prompt Handling

For generation: Pass user's image description as-is to --prompt. Only rework if clearly insufficient.

For editing: Pass editing instructions in --prompt (e.g., "add a rainbow in the sky", "make it look like a watercolor painting")

Preserve user's creative intent in both cases.

Prompt Templates (high hit-rate)

Use templates when the user is vague or when edits must be precise.

Generation template:

- “Create an image of: . Style: