Nano Banana Image Generation
Generate professional images via the Gemini CLI's nanobanana extension.
When to Use This Skill
ALWAYS use this skill when the user:
- Asks for any image, graphic, illustration, or visual
- Wants a thumbnail, featured image, or banner
- Requests icons, diagrams, or patterns
- Asks to edit, modify, or restore a photo
- Uses words like: generate, create, make, draw, design, visualize
Do NOT attempt to generate images through any other method.
Before First Use
- Verify extension is installed:
gemini extensions list | grep nanobanana - If missing, install it:
gemini extensions install https://github.com/gemini-cli-extensions/nanobanana - Verify API key is set:
[-n "$GEMINI_API_KEY"] && echo "API key configured" || echo "Missing GEMINI_API_KEY"
Command Selection
| User Request | Command |
|---|---|
| "make me a blog header" | /generate |
| "create an app icon" | /icon |
| "draw a flowchart of..." | /diagram |
| "fix this old photo" | /restore |
| "remove the background" | /edit |
| "create a repeating texture" | /pattern |
| "make a comic strip" | /story |
Available Commands
Note: Always use the --yolo flag to automatically approve all tool actions.
| Command | Use Case |
|---|---|
gemini --yolo "/generate 'prompt'" | Text-to-image generation |
gemini --yolo "/edit file.png 'instruction'" | Modify existing image |
gemini --yolo "/restore old_photo.jpg 'fix scratches'" | Repair damaged photos |
gemini --yolo "/icon 'description'" | App icons, favicons, UI elements |
gemini --yolo "/diagram 'description'" | Flowcharts, architecture diagrams |
gemini --yolo "/pattern 'description'" | Seamless textures and patterns |
gemini --yolo "/story 'description'" | Sequential/narrative images |
gemini --yolo "/nanobanana prompt" | Natural language interface |
Common Options
--yolo- Required. Auto-approve all tool actions (no confirmation prompts)--count=N- Generate N variations (1-8)--preview- Auto-open generated images--styles="style1,style2"- Apply artistic styles--format=grid|separate- Output arrangement
Common Sizes
| Use Case | Dimensions | Notes |
|---|---|---|
| YouTube thumbnail | 1280x720 | --aspect=16:9 |
| Blog featured image | 1200x630 | Social preview friendly |
| Square social | 1080x1080 | Instagram, LinkedIn |
| Twitter/X header | 1500x500 | Wide banner |
| Vertical story | 1080x1920 | --aspect=9:16 |
Model Selection
Default: gemini-2.5-flash-image (~$0.04/image)
For higher quality (4K, better reasoning):
export NANOBANANA_MODEL=gemini-3-pro-image-previewBlog Featured Image Examples
# Modern illustration style
gemini --yolo "/generate 'modern flat illustration of developer coding at laptop, purple and blue gradient background, minimalist style, no text' --preview"
# Professional photography style
gemini --yolo "/generate 'professional editorial photo of coffee cup next to laptop on wooden desk, morning sunlight, shallow depth of field, no text' --count=3"
# Tech/abstract
gemini --yolo "/generate 'abstract visualization of neural network connections, dark background with glowing blue nodes, futuristic style' --preview"Icon Generation
gemini --yolo "/icon 'minimalist app logo for productivity tool' --sizes='64,128,256,512' --type='app-icon' --corners='rounded'"Diagram Generation
gemini --yolo "/diagram 'user authentication flow with OAuth' --type='flowchart' --style='modern'"Output Location
All generated images are saved to ./nanobanana-output/ in the current directory.
Presenting Results
After generation completes:
- List contents of
./nanobanana-output/to find generated files - Present the most recent image(s) to the user
- Offer to regenerate with variations if needed
Refinements and Iterations
When the user asks for changes:
- "Try again" / "Give me options": Regenerate with
--count=3 - "Make it more [adjective]": Adjust prompt and regenerate
- "Edit this one": Use
gemini --yolo "/edit nanobanana-output/filename.png 'adjustment'" - "Different style": Add
--styles="requested_style"to the command
Prompt Tips
- Be specific: Include style, mood, colors, composition details
- Add "no text": If you don't want text rendered in the image
- Reference styles: "editorial photography", "flat illustration", "3D render", "watercolor"
- Specify aspect ratio context: "wide banner", "square thumbnail", "vertical story"
Troubleshooting
| Problem | Solution |
|---|---|
GEMINI_API_KEY not set | export GEMINI_API_KEY="your-key" |
| Extension not found | Run install command from setup section |
| Quota exceeded | Wait for reset or switch to flash model |
| Image generation failed | Check prompt for policy violations, simplify request |
| Output directory missing | Will be created automatically on first run |