Image Generation (OpenAI)

Call Gemini image models through OpenAI-compatible endpoints (/v1/images/generations and /v1/images/edits) for text-to-image and reference-image editing. Compatible with the OpenAI SDK.

Supported Models

Model	Max resolution
`gemini-2.5-flash-image`	1K only
`gemini-3-pro-image-preview`	1K / 2K / 4K
`gemini-3.1-flash-image`	512 / 1K / 2K / 4K

Authentication

Authorization: Bearer <TOKEN>
Content-Type: application/json

Text-to-image `/v1/images/generations`

Method: POST Base URL: https://api.gregapi.com/v1/images/generations

Request Parameters

Parameter	Type	Required	Default	Values	Description
`model`	string	Yes	-	Model name	`gemini-2.5-flash-image`, `gemini-3-pro-image-preview`, `gemini-3.1-flash-image`
`prompt`	string	Yes	-	-	Image description text
`n`	integer	No	1	1 only	Number of images
`size`	string	No	auto	`512` / `1K` / `2K` / `4K` or `widthxheight`	Resolution; tier format (recommended) or numeric format (legacy)
`aspect_ratio`	string	No	auto	Aspect ratio	Explicit ratio
`response_format`	string	No	`b64_json`	`b64_json` / `url`	Output format: base64 or URL

Aspect ratio values:

1:1  2:3  3:2  3:4  4:3  4:5  5:4  9:16  16:9  21:9

gemini-3.1-flash-image additionally supports 1:4, 4:1, 1:8, 8:1, 9:21.

Example

curl -X POST "https://api.gregapi.com/v1/images/generations" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "gemini-3-pro-image-preview",
  "prompt": "A futuristic cityscape at sunset with flying cars",
  "size": "2K",
  "aspect_ratio": "16:9",
  "response_format": "b64_json"
}'

Response (`response_format=b64_json`)

{
  "created": 1700000000,
  "data": [
    {
      "b64_json": "<BASE64_IMAGE_DATA>",
      "revised_prompt": "Revised prompt (if any)"
    }
  ]
}

Response (`response_format=url`)

{
  "created": 1700000000,
  "data": [
    {
      "url": "https://example.com/xxx.png"
    }
  ]
}

Billed-but-blocked error response

{
  "error": {
    "message": "no image generated (request id: 20260608235925678097275ZgRxuG4y)",
    "type": "one_hub_error",
    "code": "no_image_generated"
  },
  "usage": {
    "input_tokens": 353,
    "output_tokens": 0,
    "total_tokens": 353,
    "output_tokens_details": null,
    "input_tokens_details": {
      "text_tokens": 95,
      "image_tokens": 258
    }
  }
}

usage is only returned when the failure already incurred billable prompt/input tokens. Ordinary failures (parameter validation, quota, network) do not return usage.

Image editing `/v1/images/edits`

Method: POST (multipart/form-data) Base URL: https://api.gregapi.com/v1/images/edits

Request Parameters

Parameter	Type	Required	Default	Description
`model`	string	Yes	-	Model name
`prompt`	string	Yes	-	Editing instruction
`image`	file	No	-	Base image; mutually exclusive with `image_urls[]`
`image[]`	file[]	No	-	Reference images, up to 14
`image_urls[]`	string[]	No	-	Image URL list; first is base, rest are references; can mix with `image`/`image[]`
`size`	string	No	auto	Output resolution, `512` / `1K` / `2K` / `4K` or `widthxheight`
`aspect_ratio`	string	No	auto	Explicit aspect ratio
`response_format`	string	No	`b64_json`	`b64_json` or `url`
`mask`	file	No	-	Mask image for local editing

Notes

The first image_urls[] serves as the base image, the rest are references; up to 14 total.
Only public HTTP/HTTPS image URLs are supported; localhost and private IPs are not.
Without size, it is inferred from the base image (for gemini-3-pro-image-preview only).
An explicit aspect_ratio takes precedence when provided.

Example

curl -X POST "https://api.gregapi.com/v1/images/edits" \
  -H "Authorization: Bearer $TOKEN" \
  -F "model=gemini-3-pro-image-preview" \
  -F "prompt=Convert this image to oil-painting style" \
  -F "response_format=url" \
  -F "image=@/path/to/base.png"

Error Codes

HTTP status	Description	Solution
400	Invalid parameter	Check prompt, size format
413	Image too large	Compress reference image under 10 MB
429	Quota exceeded	Check quota or retry later

Large Language Models (LLM)

Image Models

Video Models

Speech Models

Image Generation (OpenAI)

Supported Models

Authentication

Text-to-image `/v1/images/generations`

Request Parameters

Example

Response (`response_format=b64_json`)

Response (`response_format=url`)

Billed-but-blocked error response

Image editing `/v1/images/edits`

Request Parameters

Notes

Example

Error Codes

​Supported Models

​Authentication

​Text-to-image /v1/images/generations

​Request Parameters

​Example

​Response (response_format=b64_json)

​Response (response_format=url)

​Billed-but-blocked error response

​Image editing /v1/images/edits

​Request Parameters

​Notes

​Example

​Error Codes

Supported Models

Authentication

Text-to-image `/v1/images/generations`

Request Parameters

Example

Response (`response_format=b64_json`)

Response (`response_format=url`)

Billed-but-blocked error response

Image editing `/v1/images/edits`

Request Parameters

Notes

Example

Error Codes