Nano Banana

Nano Banana (Gemini Image) is Google's family of multimodal image generation and editing models. In addition to text-to-image generation, every model supports conversational (multi-turn) image editing by passing one or more reference images alongside the prompt, interleaved image-and-text output, and Content Credentials (C2PA). All generated images carry a SynthID watermark.

POST https://llm.siraya.ai/v1/images/generations

Supported Models

Model ID	Description
`gemini-2.5-flash-image`	a.k.a. Nano Banana. Fast generation and editing. Up to 3 input images per prompt.
`gemini-3-pro-image`	a.k.a. Nano Banana Pro. Highest-quality generation and editing, with thinking and Google Search grounding. Up to 14 input images and resolutions up to 4K.
`gemini-3.1-flash-image`	a.k.a. Nano Banana 2. Fast generation and editing, with thinking and Google Search grounding. Up to 14 input images and resolutions from 512 up to 4K.
`gemini-3.1-flash-lite-image`	a.k.a. Nano Banana 2 Lite. Fastest, most cost-efficient generation and editing (~4s latency), with thinking. Up to 14 input images per prompt; 1K resolution only.

Generate Images

Generate an image from a text prompt, or edit/combine existing images by adding image to the same call.

Authorization string Required

Your API Key (e.g., `Bearer `).

Body

model string Required

The ID of the model to use (e.g. gemini-2.5-flash-image, gemini-3-pro-image, gemini-3.1-flash-image, gemini-3.1-flash-lite-image).

prompt string Required

A text description of the desired image, or instructions for how to edit/combine the images in image.

image string or array

An input image URL or base64 data URL to edit or use as a reference, or an array of them. Omit for pure text-to-image generation. See image below.

size string

The dimensions of the generated image, mapped to a supported aspect ratio internally (see Aspect Ratios & Resolutions); when omitted, the model defaults to 1:1.

async boolean Default: false

When false, the request waits for generation to finish and returns the completed image. When true, it returns immediately with an image id while generation runs in the background. There is no status/poll endpoint for images — pass callbackUrl to receive the result. See Asynchronous generation.

callbackUrl string

Only used when async is true. A URL the router will POST to once generation completes (or fails). This is the only way to retrieve the result of an async image job.

extra_body object

Additional Gemini-specific parameters merged into the request; unknown top-level fields are also automatically captured into this object, so nesting under extra_body is optional over plain HTTP. See extra_body below.

cURLPython

curl https://llm.siraya.ai/v1/images/generations \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <API_KEY>" \
  -d '{
    "model": "gemini-3-pro-image",
    "prompt": "A serene Japanese garden with a red maple tree beside a koi pond, soft morning light",
    "size": "1024x1536"
  }'

import requests

url = "https://llm.siraya.ai/v1/images/generations"
headers = {
    "Content-Type": "application/json",
    "Authorization": "Bearer <API_KEY>"
}
data = {
    "model": "gemini-3-pro-image",
    "prompt": "A serene Japanese garden with a red maple tree beside a koi pond, soft morning light",
    "size": "1024x1536"
}

response = requests.post(url, headers=headers, json=data)
print(response.json())

Example Response

Gemini Image always returns exactly one base64-encoded image per request — there is no n parameter and no url response format.

{
    "created": 1774716098,
    "data": [
        {
            "b64_json": "iVBORw0KGgoAAAANSUhEUgAA..."
        }
    ]
}

image

Pass one or more reference images to edit or combine, instead of generating from text alone. The value can be a single URL/base64 data URL, or an array of them.

{
  "model": "gemini-3-pro-image",
  "prompt": "Replace the background with a sunset beach and keep the subject unchanged",
  "image": [
    "https://resources.siraya.ai/image/example1.png"
  ]
}

gemini-2.5-flash-image accepts up to 3 images per prompt; gemini-3-pro-image, gemini-3.1-flash-image, and gemini-3.1-flash-lite-image accept up to 14, following Google's guidance for mixing reference images — allocated per category: gemini-3-pro-image up to 6 objects / 5 characters / 3 style references, gemini-3.1-flash-image up to 10 objects / 4 characters, gemini-3.1-flash-lite-image up to 5 characters.

extra_body

Nested parameters specific to Gemini Image. Pass them as a JSON object under extra_body, or — since unknown top-level fields are captured automatically — as flat keys directly in the request body.

Key	Type	Notes
`aspect_ratio`	string	Overrides the ratio derived from `size`. See Aspect Ratios & Resolutions for supported values per model.
`image_size`	string	`1K`, `2K`, or `4K`; `gemini-3.1-flash-image` also supports `512`. `gemini-3.1-flash-lite-image` only supports `1K`. Must be uppercase `K`. Default: `1K`.
`thinking`	object	Structured form — `{"type": "disabled"}` to turn off, or `{"type": "enabled", "thinking_level": "high"}` to set a tier explicitly. See thinking_level support below for exactly which values each model accepts.
`seed`	integer	Random seed for reproducibility. Even when set, determinism isn't guaranteed — identical requests with the same seed can still return different images.

{
  "model": "gemini-3.1-flash-image",
  "prompt": "A serene Japanese garden with a red maple tree beside a koi pond",
  "size": "1024x1536",
  "extra_body": {
    "aspect_ratio": "9:16",
    "thinking": {
      "type": "enabled",
      "thinking_level": "high"
    }
  }
}

`thinking_level` support

Gemini image models take a thinking_level tier (via thinking) instead of a token budget. Only two tiers exist here — minimal/high — narrower than the four tiers (minimal/low/medium/high) available on Gemini 3.x text models; sending low/medium to an image model always returns 400.

Model	Supported `thinking_level` values	Default	Notes
`gemini-2.5-flash-image`	Not supported	—	Any explicit `thinking` config returns 400.
`gemini-3-pro-image`	`high` only	`high`	Always reasons internally; an explicit value of any kind returns 400 — omit the field entirely.
`gemini-3.1-flash-image`	`minimal`, `high`	`minimal`	Omitting the field is byte-identical to sending `minimal` explicitly.
`gemini-3.1-flash-lite-image`	`minimal`, `high`	`minimal`	Same two tiers as `gemini-3.1-flash-image`.

We always set includeThoughts=true on Gemini's native thinkingConfig regardless of which tier is sent. For the equivalent breakdown across Gemini's text models, see Per-Model Details → Gemini.

Aspect Ratios & Resolutions

Gemini Image maps requested dimensions to a supported aspect ratio. Set the size parameter, extra_body.aspect_ratio, or describe the ratio you want in the prompt.

Model	Supported aspect ratios	Supported resolutions
`gemini-2.5-flash-image`	1:1, 3:2, 2:3, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9	—
`gemini-3-pro-image`	1:1, 3:2, 2:3, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9	1K, 2K, 4K (4K in Preview)
`gemini-3.1-flash-image`	1:1, 3:2, 2:3, 3:4, 1:4, 4:1, 4:3, 4:5, 5:4, 1:8, 8:1, 9:16, 16:9, 21:9, 9:21	512, 1K, 2K, 4K (4K in Preview)
`gemini-3.1-flash-lite-image`	1:1, 3:2, 2:3, 3:4, 4:3, 4:5, 5:4, 9:16, 16:9, 21:9	1K only

Model Specifications

	`gemini-2.5-flash-image`	`gemini-3-pro-image`	`gemini-3.1-flash-image`	`gemini-3.1-flash-lite-image`
Context window	32,768	65,536	131,072	65,536
Max output tokens	32,768	32,768	32,768	4,096
Max input images per prompt	3	14	14	14
Max output images per prompt	1 (no `n` parameter)	1 (no `n` parameter)	1 (no `n` parameter)	1 (no `n` parameter)
Max resolution	~1 MP	4K (~16 MP, Preview)	4K (~16 MP, Preview)	1K (~1 MP) only
Thinking	Not supported	Supported	Supported	Supported
Google Search grounding	Not supported	Supported	Supported	Not supported
Image generation from video	Not supported	Not supported	Not supported	Not supported
Interleaved image + text	Supported	Supported	Supported	Supported
Content Credentials (C2PA)	Supported	Supported	Supported	Supported
Knowledge cutoff	June 2024	January 2025	January 2025	January 2025

Supported input MIME types: image/png, image/jpeg, image/webp, image/heic, image/heif. Inline / direct-upload images are limited to 7 MB per file (30 MB when referenced from cloud storage), with a 500 MB total request input limit.

For a list of all available image models, visit the Models Directory.