nano-banana

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

1. Verify extension is installed:

   gemini extensions list | grep nanobanana
   

2. If missing, install it:

   gemini extensions install https://github.com/gemini-cli-extensions/nanobanana
   

3. 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-preview

Blog 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:

1. List contents of ./nanobanana-output/ to find generated files
2. Present the most recent image(s) to the user
3. 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

1. Be specific: Include style, mood, colors, composition details
2. Add "no text": If you don't want text rendered in the image
3. Reference styles: "editorial photography", "flat illustration", "3D render", "watercolor"
4. 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