Nano Banana Image Generation

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-2.5-flash-image

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

See 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-2.5-flash-image (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

For Consistency

When creating multiple related images:

1. Create a style guide in your prompt
2. Use the same style descriptors across prompts
3. Reference the first image when editing subsequent ones

Example Prompts

See the examples/ directory for full prompt examples.

Header/Hero Images

"Wide 16:9 header image for a technology blog. Clean minimalist design with
abstract geometric shapes in teal and orange. Bright white background,
editorial magazine aesthetic. No text, no dark colors, no gradients."

Product Photography Style

"Professional product photo of a ceramic coffee mug on a marble surface.
Soft natural lighting from the left, subtle shadow, clean white background.
Commercial photography style, 4K quality, sharp focus on the product."

Illustrations

"Whimsical children's book illustration of a fox reading a book under a
large oak tree. Soft watercolor style, warm autumn colors, gentle and
inviting mood. Simple composition with the fox as the focal point."

Icons and Logos

"Minimalist app icon for a meditation app. Simple lotus flower symbol in
a soft purple gradient. Clean geometric design, works at small sizes,
modern and calming aesthetic."

Troubleshooting

"No image in response"

• Prompt may have triggered safety filters
• Try rephrasing with less ambiguous terms
• Check if the model supports image generation

Poor quality results

• Add more specific style guidance
• Use a more capable model (gemini-2.5-flash-image)
• Be more explicit about what you want

Image doesn't match description

• Be more explicit about composition
• Add negative constraints ("no X, no Y")
• Try breaking complex prompts into simpler parts

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