nano-banana-imagegen

name	nano-banana-imagegen
description	Generate and edit images using Google Gemini image models via the nano-banana CLI. Use when the user asks to create, generate, make, or edit images with AI. Supports text-to-image, image editing, style transfer, and multi-image composition. Trigger on requests like "create an image", "generate a picture", "make me a logo", "edit this photo", "add X to this image".

Nano Banana Image Generation

Generate and edit images using Google's Gemini image models via the nano-banana CLI.

Prerequisites

• GEMINI_API_KEY environment variable must be set
• The CLI is installed via npx @the-focus-ai/nano-banana

Quick Reference

# Generate a new image
npx @the-focus-ai/nano-banana "a serene mountain landscape at sunset"

# Edit an existing image
npx @the-focus-ai/nano-banana "add a hot air balloon to the sky" --file photo.jpg

# Specify output path
npx @the-focus-ai/nano-banana "a minimalist logo" --output logo.png

# Use a specific model
npx @the-focus-ai/nano-banana "detailed illustration" --model gemini-2.0-flash-exp

Workflow

Step 1: Understand the Request

Before generating, clarify:

• Subject: What should be in the image?
• Style: Photorealistic, illustration, cartoon, abstract?
• Mood: Bright, dark, moody, cheerful?
• Composition: Close-up, wide shot, specific aspect ratio?
• Use case: Hero image, icon, social media, print?

Step 2: Craft an Effective Prompt

Read references/prompting-guide.md for comprehensive guidance.

Key principles:

1. Be specific and descriptive
2. Include style references
3. Specify what you DON'T want
4. Describe composition and framing

Example — Weak prompt:

"a cat"

Example — Strong prompt:

"A fluffy orange tabby cat curled up on a velvet armchair, soft afternoon sunlight streaming through a window, warm cozy interior, photorealistic style, shallow depth of field"

Step 3: Generate the Image

npx @the-focus-ai/nano-banana "your detailed prompt here"

Default output: output/generated-<timestamp>.png

Step 4: Iterate

If the result isn't right:

1. Refine the prompt — Add more detail or constraints
2. Edit the image — Use --file to modify the generated image
3. Try a different model — Some models handle certain styles better

Commands

Text-to-Image Generation

npx @the-focus-ai/nano-banana "<prompt>"

Image Editing

npx @the-focus-ai/nano-banana "<edit instruction>" --file <input-image>

Edit instructions should describe the change:

• "Remove the background and replace with a gradient"
• "Add sunglasses to the person"
• "Change the sky to sunset colors"
• "Make it look like a watercolor painting"

Options

Option	Description
--file <image>	Input image for editing
--output <path>	Custom output path
--model <name>	Specific Gemini model
--flash	Use gemini-2.0-flash (faster, simpler images)
--prompt-file <path>	Read prompt from file
--list-models	Show available models

Best Practices

For Better Results

1. Start with composition: Describe the layout first, then details
2. Use artistic references: "in the style of Studio Ghibli", "like a National Geographic photo"
3. Specify lighting: "golden hour lighting", "dramatic chiaroscuro", "soft diffused light"
4. Include negative guidance: Describe what to avoid in the prompt itself
5. Consider aspect ratio: The model generates square by default; describe wide/tall if needed

For Editing

1. Be specific about changes: "Add a blue butterfly to the top-left corner"
2. Preserve what works: "Keep the background unchanged, only modify the foreground"
3. Iterative refinement: Make one change at a time for better control

Environment Setup

Ensure GEMINI_API_KEY is set:

export GEMINI_API_KEY="your-api-key-here"

Or create a .env file in your project:

GEMINI_API_KEY=your-api-key-here

Troubleshooting

Problem	Solution
"No image in response"	Prompt may have triggered safety filters — rephrase
Poor quality results	Add more specific style guidance, use gemini-2.0-flash-exp
Image doesn't match description	Be more explicit about composition, add negative constraints