Helicone’s AI Gateway supports image generation through models with native image output capabilities. Use the unified OpenAI-compatible API to generate images - the Gateway handles provider-specific translations automatically.
Image generation is currently supported for Nano Banana Pro (gemini-3-pro-image-preview) via Google AI Studio. Support for additional providers will be added in future updates.
Quick Start
Chat Completions
Responses API
import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.HELICONE_API_KEY,
baseURL: "https://ai-gateway.helicone.ai/v1",
});
const response = await client.chat.completions.create({
model: "gemini-3-pro-image-preview/google-ai-studio",
messages: [
{ role: "user", content: "Generate an image of a sunset over mountains" }
],
max_tokens: 8192
});
// Access generated images
const images = response.choices[0].message.images;
import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.HELICONE_API_KEY,
baseURL: "https://ai-gateway.helicone.ai/v1",
});
const response = await client.responses.create({
model: "gemini-3-pro-image-preview/google-ai-studio",
input: "Generate an image of a sunset over mountains",
max_output_tokens: 8192
});
// Access generated images from output
const messageOutput = response.output.find(item => item.type === "message");
const imageContent = messageOutput?.content.find(c => c.type === "output_image");
Configuration
To enable image generation:
- Set the
model to one that supports image output (currently gemini-3-pro-image-preview/google-ai-studio, also known as Nano Banana Pro)
- Optionally configure
image_generation to control aspect ratio and size
Chat Completions
Responses API
{
model: "gemini-3-pro-image-preview/google-ai-studio",
messages: [...],
image_generation: {
aspect_ratio: "16:9",
image_size: "2K"
}
}
{
model: "gemini-3-pro-image-preview/google-ai-studio",
input: "...",
image_generation: {
aspect_ratio: "16:9",
image_size: "2K"
}
}
image_generation
| Parameter | Type | Description |
|---|
aspect_ratio | string | Image aspect ratio (e.g., "16:9", "1:1", "9:16") |
image_size | string | Image resolution (e.g., "2K", "1K") |
The image_generation field is optional. If omitted, the model uses default settings. However, if you specify image_generation, both aspect_ratio and image_size are required.
Handling Responses
Chat Completions
When streaming, images arrive in chunks via the images delta field:// Image chunks arrive in delta
{
"choices": [{
"delta": {
"images": [{
"type": "image_url",
"image_url": {
"url": "data:image/png;base64,iVBORw0KGgo..."
}
}]
}
}]
}
Non-streaming responses include images in the message:{
"id": "chatcmpl-abc123",
"object": "chat.completion",
"model": "gemini-3-pro-image-preview",
"choices": [{
"index": 0,
"message": {
"role": "assistant",
"content": "Here's the image you requested:",
"images": [{
"type": "image_url",
"image_url": {
"url": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA..."
}
}]
},
"finish_reason": "stop"
}],
"usage": {
"prompt_tokens": 12,
"completion_tokens": 1024,
"total_tokens": 1036
}
}
Responses API
Streaming events follow the Responses API format:// Content part added for image
{
"type": "response.content_part.added",
"item_id": "msg_abc123",
"output_index": 0,
"content_index": 0,
"part": {
"type": "output_image",
"image_url": ""
}
}
// Content part done with full image
{
"type": "response.content_part.done",
"item_id": "msg_abc123",
"output_index": 0,
"content_index": 0,
"part": {
"type": "output_image",
"image_url": "data:image/png;base64,iVBORw0KGgo..."
}
}
{
"id": "resp_abc123",
"object": "response",
"status": "completed",
"model": "gemini-3-pro-image-preview",
"output": [
{
"id": "msg_abc123",
"type": "message",
"status": "completed",
"role": "assistant",
"content": [
{
"type": "output_text",
"text": "Here's the image you requested:"
},
{
"type": "output_image",
"image_url": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA..."
}
]
}
],
"usage": {
"input_tokens": 12,
"output_tokens": 1024
}
}
Supported Models
| Model | Provider Route | Description |
|---|
gemini-3-pro-image-preview/google-ai-studio | Google AI Studio | Nano Banana Pro - Google’s multimodal model with native image generation |
