Nano Banana 2 - Image Generation API

Generate images from text prompts or edit existing images using Google Nano Banana 2 (Gemini 3.1 Flash — gemini-3.1-flash-image-preview).

Key capabilities:

• Multi-size output: 512px, 1K, 2K, 4K
• Improved text rendering
• Multi-image input for editing and style transfer
• Multiple aspect ratios (1:1, 16:9, 9:16, etc.)

Authentication

IMPORTANT: All API requests require authentication. Get your auth token and API URL by running:

AUTH_TOKEN=$(/home/user/.local/bin/rebyte-auth)
API_URL=$(python3 -c "import json; print(json.load(open('/home/user/.rebyte.ai/auth.json'))['sandbox']['relay_url'])")

Include the token in all API requests as a Bearer token, and use $API_URL as the base for all API endpoints.

Text-to-Image Generation

Create an image from a text description.

curl -X POST "$API_URL/api/data/images/generate" \
  -H "Authorization: Bearer $AUTH_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A futuristic cityscape at sunset with flying cars",
    "aspectRatio": "16:9",
    "imageSize": "2K"
  }'

---

Image-to-Image Generation

Edit, enhance, or transform an existing image by providing it as base64.

curl -X POST "$API_URL/api/data/images/generate" \
  -H "Authorization: Bearer $AUTH_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Transform this into a watercolor painting style",
    "image": "<base64-encoded-image>",
    "imageMimeType": "image/png"
  }'

Use Cases:

• Style Transfer: "Make this photo look like a Van Gogh painting"
• Enhancement: "Improve the lighting and colors"
• Editing: "Remove the background and replace with a beach scene"
• Text Correction: "Fix the text in this image: change 'Helo' to 'Hello'"

---

Parameters

Name	Type	Required	Default	Description
prompt	string	Yes	-	Text description or editing instructions
image	string	No	-	Base64-encoded source image (for image-to-image)
imageMimeType	string	No	image/png	MIME type: image/png, image/jpeg, image/webp
aspectRatio	string	No	1:1	Output aspect ratio
imageSize	string	No	1K	Output size: 512, 1K, 2K, or 4K

Aspect Ratios:

Ratio	Use Case
1:1	Square (social media, icons)
16:9	Landscape (presentations, banners)
9:16	Portrait (mobile, stories)
4:3	Standard landscape
3:4	Standard portrait
21:9	Ultra-wide (cinematic)
4:1, 8:1	Extreme landscape (panoramic)
1:4, 1:8	Extreme portrait (tall banners)
2:3, 3:2, 4:5, 5:4	Various formats

Image Sizes:

Size	Resolution	Best For
512	512px	Quick previews, thumbnails
1K	~1024px	Standard web use (default)
2K	~2048px	High-quality web, presentations
4K	~4096px	Print, final assets

---

Response

{
  "image": {
    "base64": "iVBORw0KGgoAAAANSUhEUgAA...",
    "mimeType": "image/png",
    "dataUrl": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA..."
  },
  "description": "A vibrant futuristic cityscape..."
}

Field	Description
image.base64	Base64-encoded image data
image.mimeType	Image MIME type (typically image/png)
image.dataUrl	Ready-to-use data URL for HTML/CSS
description	Model's description of the generated image

---

Using with Python

import subprocess
import requests
import base64
import json
from pathlib import Path

# Get auth token and API URL
AUTH_TOKEN = subprocess.check_output(["/home/user/.local/bin/rebyte-auth"]).decode().strip()
with open('/home/user/.rebyte.ai/auth.json') as f:
    API_URL = json.load(f)['sandbox']['relay_url']

HEADERS = {"Authorization": f"Bearer {AUTH_TOKEN}"}

def generate_image(
    prompt: str,
    image_path: str = None,
    aspect_ratio: str = "1:1",
    image_size: str = "1K"
) -> dict:
    """Generate an image from text, or edit an existing image."""
    payload = {
        "prompt": prompt,
        "aspectRatio": aspect_ratio,
        "imageSize": image_size
    }

    # Add source image for image-to-image
    if image_path:
        image_data = Path(image_path).read_bytes()
        payload["image"] = base64.b64encode(image_data).decode()
        # Detect mime type from extension
        ext = Path(image_path).suffix.lower()
        mime_map = {'.png': 'image/png', '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg', '.webp': 'image/webp'}
        payload["imageMimeType"] = mime_map.get(ext, 'image/png')

    response = requests.post(
        f"{API_URL}/api/data/images/generate",
        headers=HEADERS,
        json=payload
    )
    return response.json()

def save_image(result: dict, filepath: str) -> None:
    """Save generated image to a file."""
    if "image" in result:
        image_data = base64.b64decode(result["image"]["base64"])
        Path(filepath).write_bytes(image_data)
        print(f"Saved to {filepath}")
    else:
        print(f"Error: {result.get('error', 'Unknown error')}")

# Example 1: Text-to-image
result = generate_image(
    prompt="A serene mountain landscape at dawn with mist in the valley",
    aspect_ratio="16:9"
)
save_image(result, "landscape.png")

# Example 2: Image-to-image (style transfer)
result = generate_image(
    prompt="Transform this into a watercolor painting",
    image_path="photo.jpg",
    image_size="2K"
)
save_image(result, "watercolor.png")

# Example 3: High-resolution output
result = generate_image(
    prompt="A detailed botanical illustration of a rose",
    image_size="4K"
)
save_image(result, "rose_4k.png")

---

Using with Node.js

const fs = require('fs');
const path = require('path');
const { execSync } = require('child_process');

// Get auth token and API URL
const AUTH_TOKEN = execSync('/home/user/.local/bin/rebyte-auth').toString().trim();
const authConfig = JSON.parse(fs.readFileSync('/home/user/.rebyte.ai/auth.json'));
const API_URL = authConfig.sandbox.relay_url;

async function generateImage(prompt, options = {}) {
  const payload = {
    prompt,
    aspectRatio: options.aspectRatio || '1:1',
    imageSize: options.imageSize || '1K'
  };

  // Add source image for image-to-image
  if (options.imagePath) {
    const imageBuffer = fs.readFileSync(options.imagePath);
    payload.image = imageBuffer.toString('base64');
    const ext = path.extname(options.imagePath).toLowerCase();
    const mimeMap = {'.png': 'image/png', '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg', '.webp': 'image/webp'};
    payload.imageMimeType = mimeMap[ext] || 'image/png';
  }

  const response = await fetch(`${API_URL}/api/data/images/generate`, {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${AUTH_TOKEN}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(payload)
  });
  return response.json();
}

function saveImage(result, filepath) {
  if (result.image) {
    const buffer = Buffer.from(result.image.base64, 'base64');
    fs.writeFileSync(filepath, buffer);
    console.log(`Saved to ${filepath}`);
  } else {
    console.error('Error:', result.error || 'Unknown error');
  }
}

// Example: Text-to-image
(async () => {
  const result = await generateImage(
    'A neon-lit cyberpunk street scene at night',
    { aspectRatio: '21:9', imageSize: '2K' }
  );
  saveImage(result, 'cyberpunk.png');
})();

// Example: Image-to-image
(async () => {
  const result = await generateImage(
    'Make this look like a Studio Ghibli animation',
    { imagePath: 'photo.jpg', imageSize: '2K' }
  );
  saveImage(result, 'ghibli_style.png');
})();

---

Prompt Tips

Text-to-Image

Bad:  "A dog"
Good: "A golden retriever puppy playing in autumn leaves, warm sunlight"

Image-to-Image

Style Transfer: "Transform into oil painting style", "Make it look like anime"
Enhancement: "Improve lighting and contrast", "Make colors more vibrant"
Editing: "Remove the person in the background", "Add a rainbow to the sky"
Text Fix: "Change the text from 'Helo' to 'Hello'"

---

Error Handling

Missing or Invalid Auth Token:

{
  "error": "Missing sandbox token"
}

Solution: Run rebyte-auth and include the token in your request.

No Image Generated:

{
  "error": "No image generated",
  "message": "SAFETY"
}

This occurs when the prompt triggers content safety filters.

---

Delivering Output

After generating images, upload them to the Artifact Store so the user can access them.

Important Notes

• All generated images include invisible SynthID watermarking
• Images are generated server-side; base64 responses can be large
• Use imageSize to control quality/speed tradeoff: 512 for fast previews, 4K for final assets
• Content safety filters may block certain prompts
• For image-to-image, the source image is sent as base64 in the request body