Gemini 3.1 Flash Image

Google’s Gemini 3.1 Flash Image for AI image generation and editing via Gemini API.

Gemini 3.1 Flash Image is Google’s image generation model, available through AnyFast via the native Gemini API. It can generate images from text prompts and edit existing images using a reference photo.

Google released gemini-3.1-flash-image as the GA model for Nano Banana 2 on May 28, 2026. Use this stable model ID instead of gemini-3.1-flash-image-preview, which is deprecated and scheduled to shut down on June 25, 2026.

Key capabilities

• Text-to-image — Generate images from text descriptions
• Image editing — Pass a reference image in inline_data alongside your text instruction
• Aspect ratio control — 1:1, 4:3, 3:4, 16:9, 9:16
• Resolution control — 512 (512px), 1K (~1024px), 2K (~2048px), 4K (~4096px) on the long edge
• Multi-modal output — Return both the image and a text caption with responseModalities: ["TEXT", "IMAGE"]

Note: If you need the generated image returned as a URL, select the Aggregate-NanoUrl group when creating your API token.

Text-to-image example

cURL

curl "https://www.anyfast.ai/v1beta/models/gemini-3.1-flash-image:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          { "text": "Generate an image of a sunset over mountains" }
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["TEXT", "IMAGE"],
      "imageConfig": {
        "aspectRatio": "16:9",
        "imageSize": "1K"
      }
    }
  }'

Image editing example (with reference image)

Include both a text instruction and an inline_data reference image in the same parts array.

cURL

# First encode your image to base64:
# BASE64=$(base64 -i your_photo.jpg)
#
# Then send the request:
curl "https://www.anyfast.ai/v1beta/models/gemini-3.1-flash-image:generateContent?key=YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [
      {
        "role": "user",
        "parts": [
          {
            "text": "Hi, this is a picture of me. Can you add a llama next to me?"
          },
          {
            "inline_data": {
              "mime_type": "image/jpeg",
              "data": "<YOUR_BASE64_ENCODED_IMAGE>"
            }
          }
        ]
      }
    ],
    "generationConfig": {
      "responseModalities": ["TEXT", "IMAGE"],
      "imageConfig": {
        "aspectRatio": "1:1",
        "imageSize": "1K"
      }
    }
  }'

Parameters

Parameter	Type	Required	Description
key	string	Yes	API key (query parameter)
contents[].parts[].text	string	Yes	Text prompt or instruction
contents[].parts[].inline_data.mime_type	string	No	Reference image type: image/jpeg, image/png, image/webp
contents[].parts[].inline_data.data	string	No	Base64-encoded reference image
generationConfig.responseModalities	array	Yes	["IMAGE"] or ["TEXT", "IMAGE"]
generationConfig.imageConfig.aspectRatio	string	No	1:1 / 4:3 / 3:4 / 16:9 / 9:16
generationConfig.imageConfig.imageSize	string	No	512 / 1K / 2K / 4K (default: 1K)

API Reference

View the interactive API playground for Gemini 3.1 Flash Image.