Gemini 3 Pro Image parameters

Use the stable model ID:

gemini-3-pro-image

Do not use the retired gemini-3-pro-image-preview ID.

Output controls

Field	Value through this API
`responseModalities`	Include `IMAGE`; `TEXT` is optional
`candidateCount`	Omit or use `1`
`imageSize`	Omit for 1K, or use uppercase `1K`, `2K`, `4K`
`aspectRatio`	Optional; choose one value below
Top-level `n` or `resolution`	Not supported

Supported ratios:

1:1   2:3   3:2   3:4   4:3
4:5   5:4   9:16  16:9  21:9

The model-specific API contract exposes the complete ratio and size matrix above. Use only those values in requests.

4K generation body

{
  "contents": [{
    "role": "user",
    "parts": [{"text": "A precise museum exhibition poster with a disciplined grid"}]
  }],
  "generationConfig": {
    "responseModalities": ["TEXT", "IMAGE"],
    "imageConfig": {"aspectRatio": "4:3", "imageSize": "4K"},
    "candidateCount": 1
  }
}

Editing body

{
  "contents": [{
    "role": "user",
    "parts": [
      {"text": "Preserve the product and replace the surface with dark marble"},
      {
        "inlineData": {
          "mimeType": "image/jpeg",
          "data": "BASE64_SOURCE_IMAGE_1"
        }
      },
      {"inlineData": {"mimeType": "image/png", "data": "BASE64_SOURCE_IMAGE_2"}}
    ]
  }],
  "generationConfig": {
    "responseModalities": ["TEXT", "IMAGE"],
    "imageConfig": {"aspectRatio": "1:1", "imageSize": "1K"},
    "candidateCount": 1
  }
}

Repeat inlineData for multiple references. Unified asynchronous editing accepts 1–16 images, with a 20 MiB decoded limit per file and 64 MiB total. Search grounding and broader tool behavior still follow the selected official model’s current support. A fixed maximum source-image byte or pixel size is not currently published. Total request-body, proxy, and upstream limits may differ; reduce the source image after HTTP 413, and contact API support before relying on a guaranteed production envelope.

Transport and logging

A 4K response can carry several megabytes of decoded image data and a larger Base64 string. Set request, proxy, memory, and log limits accordingly. Never write the full Base64 payload into normal application logs.

Run complete Pro examples

Generate, queue, edit, and handle the returned MIME.

Review exact prices

Compare Pro with Flash using current YingTu rates.

​Output controls

​4K generation body

​Editing body

​Transport and logging