Image generation

Use openai/gpt-image-2 to generate images from a text prompt. POST /v1/images/generations accepts OpenAI’s Images API shape and returns base64-encoded image bytes — the model never returns URLs.

Generate an image

curl https://api.impossibl.com/v1/images/generations \
  -H "Authorization: Bearer imp-rt-..." \
  -H 'content-type: application/json' \
  -d '{
    "model": "openai/gpt-image-2",
    "prompt": "A watercolor lighthouse at dawn",
    "size": "1024x1024"
  }'

Response (abridged)

{
  "created": 1785300000,
  "data": [{ "b64_json": "iVBORw0KGgo..." }],
  "usage": {
    "total_tokens": 214,
    "input_tokens": 18,
    "output_tokens": 196,
    "input_tokens_details": { "text_tokens": 18, "image_tokens": 0 }
  }
}

Decode data[0].b64_json to get the image file. A revised_prompt field accompanies an image when the provider rewrote your prompt before generating.

Options

Field	Values
`n`	number of images to generate, default 1
`size`	`"{width}x{height}"` (e.g. `1024x1024`, `1536x1024`) or `"auto"`
`quality`	`auto`, `low`, `medium`, `high`, `standard`, `hd`
`background`	`auto`, `transparent`, `opaque`
`output_format`	`png`, `jpeg`, `webp`
`output_compression`	`0`–`100` (JPEG/WebP only)
`user`	stable per-user id forwarded to the provider for abuse monitoring

Billing

Image output is billed per token like any other model — text input tokens plus image output tokens, at the rates in Models & pricing (

5.00 /

30.00 per 1M for openai/gpt-image-2). The cost is settled when generation finishes and appears in GET /v1/usage and the request log. Two guardrails to know:

Model and endpoint must match: sending an image model to a text endpoint (/v1/chat/completions, etc.) fails with 400 invalid_request_error, as does sending a text model to the images endpoint.
Image generation always draws on the prepaid balance — there is no BYOK path for it yet, so an empty balance returns 402 even with a provider credential configured.

Get started

Core concepts

Using the API

Generate an image

Options

Billing

​Generate an image

​Options

​Billing

Generate an image

Options

Billing