Gemini 3 Pro Image 参数

{
  "contents": [{"role": "user", "parts": [{"text": "网格严谨、文字区域清楚的展览海报"}]}],
  "generationConfig": {
    "responseModalities": ["TEXT", "IMAGE"],
    "imageConfig": {"aspectRatio": "1:1", "imageSize": "4K"}
  }
}