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Model ID 
gemini-3.1-flash-image-preview

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Gemini 3.1 Flash Image Preview API Usage Guide

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Overview

Gemini 3.1 Flash Image Preview is optimized for image understanding and generation, balancing speed and cost. It supports text-to-image, image-guided editing, and multi-turn iterative workflows via contents. Reference: https://docs.cloud.google.com/vertex-ai/generative-ai/docs/models/gemini/3-1-flash-image

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Authentication

All API requests require authentication using an API key. Include your API key in the Authorization header: 
Authorization: Bearer YOUR_API_KEY

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Submit Image Generation Request

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Base URL

https://console.gmicloud.ai

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Endpoint

POST /api/v1/ie/requestqueue/apikey/requests

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Request Format

curl -X POST "https://console.gmicloud.ai/api/v1/ie/requestqueue/apikey/requests" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-flash-image-preview",
    "payload": {
      "prompt": "A hyperrealistic portrait of a cyberpunk woman under neon lights",
      "image": [
        "https://example.com/ref1.jpg",
        "https://example.com/ref2.jpg"
      ],
      "image_size": "1K",
      "aspect_ratio": "4:5"
    }
  }'

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Request Parameters

ParameterTypeRequiredDescriptionDefaultConstraints
promptstringYes (single-turn)Text description of the target image.-Required when contents is not provided
imagestring/arrayNoOptional reference image URLs for image-guided generation/editing.-Max 14 images; PNG/JPEG/WebP/HEIC/HEIF; 7MB inline upload, 30MB via GCS
image_sizestringNoOutput resolution preset for generated image.”1K”Options: “512”, “1K”, “2K”, “4K”
aspect_ratiostringNoAspect ratio of the generated image.”1:1”Options: “1:1”, “3:2”, “2:3”, “3:4”, “4:3”, “4:5”, “5:4”, “9:16”, “16:9”, “21:9”
image_output_formatstringNoOutput image format.”png”Options: “png”, “jpeg”
contentsarrayNoMulti-turn conversation payload for iterative editing.-When provided, prompt and image are ignored

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Response

{
  "request_id": "7eaa77fc-bc67-4021-9f1b-96b3fd832314",
  "model": "gemini-3.1-flash-image-preview",
  "status": "queued",
  "created_at": 1761763441,
  "updated_at": 1761763441,
  "queued_at": 1761763441
}

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Check Request Status

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Endpoint

GET /api/v1/ie/requestqueue/apikey/requests/{request_id}

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Example

curl -X GET "https://console.gmicloud.ai/api/v1/ie/requestqueue/apikey/requests/7eaa77fc-bc67-4021-9f1b-96b3fd832314" \
  -H "Authorization: Bearer YOUR_API_KEY"

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Response

{
  "request_id": "7eaa77fc-bc67-4021-9f1b-96b3fd832314",
  "model": "gemini-3.1-flash-image-preview",
  "status": "success",
  "payload": {
    "prompt": "A hyperrealistic portrait of a cyberpunk woman under neon lights",
    "image": [
      "https://example.com/ref1.jpg",
      "https://example.com/ref2.jpg"
    ],
    "image_size": "1K",
    "aspect_ratio": "4:5"
  },
  "outcome": {
    "media_urls": [
      {
        "id": "0",
        "url": "https://storage.googleapis.com/gmi-generated-assets/.../gemini_output_0.png"
      }
    ]
  },
  "created_at": 1761763441,
  "updated_at": 1761763451,
  "queued_at": 1761763441
}

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Request Status Values

StatusDescription
queuedRequest is waiting to be processed
processingImage generation is in progress
successImage generation completed successfully
failedImage generation failed
cancelledRequest was cancelled

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List Your Requests

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Endpoint

GET /api/v1/ie/requestqueue/apikey/requests?model_id=gemini-3.1-flash-image-preview

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Example

curl -X GET "https://console.gmicloud.ai/api/v1/ie/requestqueue/apikey/requests?model_id=gemini-3.1-flash-image-preview" \
  -H "Authorization: Bearer YOUR_API_KEY"

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Get Model Information

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Endpoint

GET /api/v1/ie/requestqueue/apikey/models/gemini-3.1-flash-image-preview

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Example

curl -X GET "https://console.gmicloud.ai/api/v1/ie/requestqueue/apikey/models/gemini-3.1-flash-image-preview" \
  -H "Authorization: Bearer YOUR_API_KEY"

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List Available Models

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Endpoint

GET /api/v1/apikey/models

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Example

curl -X GET "https://console.gmicloud.ai/api/v1/apikey/models" \
  -H "Authorization: Bearer YOUR_API_KEY"

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Multi-turn Conversation (Iterative Image Editing)

This model supports multi-turn conversations for iterative image editing. After generating an image, you can continue refining it by providing additional instructions.

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How It Works

  1. First Turn: Send a regular request with prompt (and optional image)
  2. Response: The response includes next_turn_contents with prior conversation context
  3. Next Turn: Copy next_turn_contents into payload contents, then append your new user instruction
  4. Repeat: Continue until the result is satisfactory

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Model Specifications

SpecificationValue
Model IDgemini-3.1-flash-image-preview
Max input tokens131,072
Max output tokens32,768
Max input images14
Max file size (inline upload)7 MB
Max file size (GCS)30 MB
Max input size500 MB
Supported image MIME typesimage/png, image/jpeg, image/webp, image/heic, image/heif
Supported aspect ratios1:1, 3:2, 2:3, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9
Temperature0.0-2.0 (default 1.0)
topP0.0-1.0 (default 0.95)
candidateCount1

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Capabilities

  • Supported: System instructions, Count Tokens, Thinking
  • Not supported: Code execution, Function calling, Gemini Live API, implicit/explicit context caching, Vertex AI RAG Engine, Chat completions

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Tips for Better Results

  1. Use specific and descriptive prompts for stable outputs.
  2. For complex edits, use multi-turn mode with contents for iterative refinement.