Nano Banana Pro

Generate/edit images with Nano Banana Pro (Gemini 3 Pro Image). Use for image create/modify requests incl. edits. Supports text-to-image + image-to-image; 1K/2K/4K; use --input-image.

Security Scan

The skill appears to implement an image-generation tool for Gemini as described, but the registry metadata omits required items (an API key and the 'uv' runner) and there are small inconsistencies that you should resolve before trusting it.

Purpose & Capability

Name and description match the included script: it calls Google's GenAI client to generate/edit images and uses Pillow to save PNGs. However, the registry metadata claims no required env vars or binaries while the script and SKILL.md clearly depend on an API key (GEMINI_API_KEY or --api-key) and on the 'uv' runner; that mismatch is inconsistent and should be corrected.

Instruction Scope

SKILL.md instructions are narrowly focused on image generation/editing: how to run the script, resolution mapping, filename conventions, and preflight checks. The instructions and script do not request unrelated files, credentials, or send data to unexpected endpoints beyond the GenAI client. They do instruct saving output into the user's current working directory (explicit) which is expected for this use case.

Install Mechanism

No install/spec is provided (instruction-only with an included Python script). The script lists dependencies (google-genai, pillow) in comments but there is no automated install step; this lowers installer risk but means the environment must separately install those packages. No downloads from unknown URLs are present.

Credentials

The script requires an API key (GEMINI_API_KEY or --api-key) but the skill metadata does not declare any required environment variables or primary credential. SKILL.md also expects the 'uv' binary to be present but the registry lists no required binaries. These omissions are an incoherence that could mislead users about what secrets/integations are needed.

Persistence & Privilege

The skill does not request always:true and does not modify other skills or global settings. It writes generated images to the current working directory (expected behavior) but has no extra persistence or elevated privileges beyond normal file writes.

What to consider before installing

This skill's behavior (calling Google GenAI and saving PNGs) matches its description, but the registry metadata omits two important requirements: - The Python script requires a Gemini API key (GEMINI_API_KEY or --api-key). The skill metadata should declare this; verify you are comfortable providing such a key and that it is scoped/ephemeral if possible. - The SKILL.md instructs running the script with the 'uv' runner, but the registry lists no required binaries. Confirm you have a trustworthy 'uv' binary and understand how it runs the script. Before installing or using the skill: - Ask the publisher for a homepage/source and request corrected metadata that lists GEMINI_API_KEY and the 'uv' runtime requirement. - Inspect or run the script in a sandboxed environment first. The code is short and readable, but it will send prompts and any provided input images to the Google GenAI client and will create files in the current working directory. - Avoid exposing highly privileged credentials. Prefer passing a limited-scope or ephemeral API key via the --api-key argument rather than relying on long-lived environment variables when possible. - Ensure required Python dependencies (google-genai, pillow) are installed from official sources before running. Given the metadata omissions, treat this as suspicious until the origin and declared requirements are clarified.

Nano Banana Pro Image Generation & Editing

Generate new images or edit existing ones using Google's Nano Banana Pro API (Gemini 3 Pro Image).

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 "<draft 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 "<final prompt>" --filename "yyyy-mm-dd-hh-mm-ss-final.png" --resolution 4K

Resolution Options

The Gemini 3 Pro 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: <subject>. Style: <style>. Composition: <camera/shot>. Lighting: <lighting>. Background: <background>. Color palette: <palette>. Avoid: <list>.”

• Editing template (preserve everything else):

  • “Change ONLY: <single change>. Keep identical: subject, composition/crop, pose, lighting, color palette, background, text, and overall style. Do not add new objects. If text exists, keep it unchanged.”

Output

• Saves PNG to current directory (or specified path if filename includes directory)
• Script outputs the full path to the generated image
• Do not read the image back - just inform the user of the saved path

Examples

Generate new image:

uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "A serene Japanese garden with cherry blossoms" --filename "2025-11-23-14-23-05-japanese-garden.png" --resolution 4K

Edit existing image:

uv run ~/.codex/skills/nano-banana-pro/scripts/generate_image.py --prompt "make the sky more dramatic with storm clouds" --filename "2025-11-23-14-25-30-dramatic-sky.png" --input-image "original-photo.jpg" --resolution 2K