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-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:

• 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