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On this page
Images
The image models in the catalogue, the request and what comes back.
POST https://api.sylphx.ai/v1/images/generations generates images from a prompt and
answers one JSON document.
#The image models
These are the image models in the catalogue:
| Model id | Name |
|---|---|
google/gemini-3-pro-image | Nano Banana Pro |
google/gemini-3.1-flash-image | Nano Banana 2 |
google/gemini-3.1-flash-lite-image | Nano Banana 2 Lite |
openai/gpt-5.4-image-2 | GPT-5.4 Image 2 |
The catalogue is the only list: GET https://api.sylphx.ai/v1/public/models shows
exactly what is served, and another model id answers 404 model_not_found.
#Request
curl https://api.sylphx.ai/v1/images/generations \
-H "Authorization: Bearer $SYLPHX_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "google/gemini-3.1-flash-image",
"prompt": "A lighthouse on a cliff at dusk, painted in gouache",
"aspect_ratio": "16:9",
"response_format": "b64_json"
}'| Field | Type | What it is |
|---|---|---|
model | string | An image model id from the catalogue. Required. |
prompt | string | What to draw, up to 32,000 characters. Required. |
n | integer | How many images, 1 to 4. Default 1. |
size | string | Width x height, for example 1024x1024, 1792x1024 or 1024x1792. Each edge is 64 to 4096. auto leaves the size to the model. Default 1024x1024. |
aspect_ratio | string | auto, 1:1, 3:2, 2:3, 4:3, 3:4, 16:9, 9:16, 21:9 or 9:21. |
quality | string | auto, low, medium, high, standard or hd. |
response_format | string | url (the default) or b64_json. |
background, output_format, output_compression, moderation | string or integer | Passed to the model that serves the request: background is auto, transparent or opaque; output_format is auto, png, webp, jpeg or svg; output_compression is 0 to 100; moderation is auto or low. Each model honours the subset it supports. |
The request is strict: an unknown key is refused with a typed invalid_request
that names its path.
#Response
{
"created": 1790000000,
"model": "google/gemini-3.1-flash-image",
"data": [{ "b64_json": "…" }]
}model is the catalogue id that served the request, never a provider's
internal name. Each data item carries url or b64_json, as you asked.
Only generation is served. POST /images/edits and POST /images/variations
answer 410.