Gemini 3.1 Flash Image Preview

Gemini 3.1 Flash Image Preview is an image generation model from Google. Call gemini-3.1-flash-image-preview through MixRoute’s native Gemini endpoint; an OpenAI-compatible endpoint is also supported.

Key capabilities

Text-to-image - Produces image output from text
Native Gemini API - Uses generateContent
Image output - Requests IMAGE in responseModalities
Content parts - Supports Gemini multimodal input structure

Output specifications

Property	Value
Endpoint	`/v1/models/gemini-3.1-flash-image-preview:generateContent`
Output modality	`IMAGE`
Response	Image data in Gemini content parts

Quick example

Gemini native API

cURL
Python

curl "https://api.mixroute.ai/v1/models/gemini-3.1-flash-image-preview:generateContent" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "contents": [
    {
      "parts": [
        {
          "text": "A minimal red circle centered on a white background"
        }
      ]
    }
  ],
  "generationConfig": {
    "responseModalities": [
      "TEXT",
      "IMAGE"
    ]
  }
}'

import requests

response = requests.post(
    "https://api.mixroute.ai/v1/models/gemini-3.1-flash-image-preview:generateContent",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    json={'contents': [{'parts': [{'text': 'A minimal red circle centered on a white '
                                           'background'}]}],
          'generationConfig': {'responseModalities': ['TEXT', 'IMAGE']}},
)

print(response.json())

OpenAI-compatible API

cURL
Python
Streaming

curl "https://api.mixroute.ai/v1/chat/completions" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "gemini-3.1-flash-image-preview",
  "messages": [
    {
      "role": "user",
      "content": "Explain quantum entanglement in simple terms."
    }
  ],
  "max_tokens": 256
}'

from openai import OpenAI

client = OpenAI(api_key="YOUR_API_KEY", base_url="https://api.mixroute.ai/v1")

response = client.chat.completions.create(
    model="gemini-3.1-flash-image-preview",
    messages=[{"role": "user", "content": "Explain quantum entanglement in simple terms."}],
    max_tokens=256,
)

print(response.choices[0].message.content)

from openai import OpenAI

client = OpenAI(api_key="YOUR_API_KEY", base_url="https://api.mixroute.ai/v1")

stream = client.chat.completions.create(
    model="gemini-3.1-flash-image-preview",
    messages=[{"role": "user", "content": "Write a short poem about the sea."}],
    max_tokens=256,
    stream=True,
)

for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="")

Parameters

Parameter	Type	Required	Description
`contents`	array	Yes	Prompt and optional multimodal content parts.
`generationConfig.responseModalities`	array	Yes	Include IMAGE to request image output.
`generationConfig`	object	No	Additional generation settings.

Home

Model Introduction

Gemini 3.1 Flash Image Preview

Key capabilities

Output specifications

Quick example

Gemini native API

OpenAI-compatible API

Parameters

​Key capabilities

​Output specifications

​Quick example

​Gemini native API

​OpenAI-compatible API

​Parameters

Key capabilities

Output specifications

Quick example

Gemini native API

OpenAI-compatible API

Parameters