Nano Banana Pro Image Generation & Editing
Generate new images or edit existing ones using the grsai.com Nano Banana Pro API.
Usage
Run the script using absolute path (do NOT cd to skill directory first):
Generate new image:
uv run scripts/generate_image.py --prompt "your image description" --filename "output-name.png" [--resolution 1K|2K|4K] [--api-key KEY]Edit existing image:
uv run 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 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 scripts/generate_image.py --prompt "<final prompt>" --filename "yyyy-mm-dd-hh-mm-ss-final.png" --resolution 4K
Resolution Options
- 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
Aspect Ratio Options
Pass via --aspect-ratio. Supported values: auto (default), 1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3, 5:4, 4:5, 21:9
API Key
The script checks for API key in this order:
--api-keyargument (use if user provided key in chat)GRSAI_API_KEYenvironment variable
If neither is available, the script exits with an error message.
Troubleshooting
| Symptom | Resolution | |
|---|---|---|
Error: No API key provided. | Set GRSAI_API_KEY env var or pass --api-key | |
Error: Input image not found: | Wrong path or unreadable file; verify with test -f "path" | |
| HTTP 401 | Wrong or expired API key | |
Generation failed: | Content moderation or invalid input; rephrase prompt | |
uv: command not found | Install: `curl -LsSf https://astral.sh/uv/install.sh \ | sh`, then restart terminal |
For transient errors (network timeouts, server errors), the script retries automatically with exponential backoff. If all retries fail, surface the error to the user.
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:
- Check if they provide an image path or reference an image in the current directory
- Use
--input-imageparameter with the path to the image - The prompt should contain editing instructions (e.g., "make the sky more dramatic", "remove the person", "change to cartoon style")
- 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:. Composition: <camera/shot>. Lighting:. Background:. Color palette:. Avoid:."
- Editing template (preserve everything else):
- "Change ONLY:. 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 image 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 scripts/generate_image.py --prompt "A serene Japanese garden with cherry blossoms" --filename "2025-11-23-14-23-05-japanese-garden.png" --resolution 4KEdit existing image:
uv run 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