feat(nano-banana-pro): add --aspect-ratio flag to generate_image.py (#28159)

* feat(nano-banana-pro): add --aspect-ratio flag to generate_image.py

* Nano Banana: allow all supported aspect ratios

* Docs: expand nano banana aspect ratio options

---------

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

skills/nano-banana-pro/SKILL.md

@@ -50,9 +50,16 @@ API key
 - `GEMINI_API_KEY` env var
 - Or set `skills."nano-banana-pro".apiKey` / `skills."nano-banana-pro".env.GEMINI_API_KEY` in `~/.openclaw/openclaw.json`
 
+Specific aspect ratio (optional)
+
+```bash
+uv run {baseDir}/scripts/generate_image.py --prompt "portrait photo" --filename "output.png" --aspect-ratio 9:16
+```
+
 Notes
 
 - Resolutions: `1K` (default), `2K`, `4K`.
+- Aspect ratios: `1:1`, `2:3`, `3:2`, `3:4`, `4:3`, `4:5`, `5:4`, `9:16`, `16:9`, `21:9`. Without `--aspect-ratio` / `-a`, the model picks freely - use this flag for avatars, profile pics, or consistent batch generation.
 - Use timestamps in filenames: `yyyy-mm-dd-hh-mm-ss-name.png`.
 - The script prints a `MEDIA:` line for OpenClaw to auto-attach on supported chat providers.
 - Do not read the image back; report the saved path only.

skills/nano-banana-pro/scripts/generate_image.py

@@ -21,6 +21,19 @@ import os
 import sys
 from pathlib import Path
 
+SUPPORTED_ASPECT_RATIOS = [
+    "1:1",
+    "2:3",
+    "3:2",
+    "3:4",
+    "4:3",
+    "4:5",
+    "5:4",
+    "9:16",
+    "16:9",
+    "21:9",
+]
+
 
 def get_api_key(provided_key: str | None) -> str | None:
     """Get API key from argument first, then environment."""
@@ -56,6 +69,12 @@ def main():
         default="1K",
         help="Output resolution: 1K (default), 2K, or 4K"
     )
+    parser.add_argument(
+        "--aspect-ratio", "-a",
+        choices=SUPPORTED_ASPECT_RATIOS,
+        default=None,
+        help=f"Output aspect ratio (default: model decides). Options: {', '.join(SUPPORTED_ASPECT_RATIOS)}"
+    )
     parser.add_argument(
         "--api-key", "-k",
         help="Gemini API key (overrides GEMINI_API_KEY env var)"
@@ -127,14 +146,17 @@ def main():
         print(f"Generating image with resolution {output_resolution}...")
 
     try:
+        # Build image config with optional aspect ratio
+        image_cfg_kwargs = {"image_size": output_resolution}
+        if args.aspect_ratio:
+            image_cfg_kwargs["aspect_ratio"] = args.aspect_ratio
+
         response = client.models.generate_content(
             model="gemini-3-pro-image-preview",
             contents=contents,
             config=types.GenerateContentConfig(
                 response_modalities=["TEXT", "IMAGE"],
-                image_config=types.ImageConfig(
-                    image_size=output_resolution
-                )
+                image_config=types.ImageConfig(**image_cfg_kwargs)
             )
         )