black-forest-labs/flux-kontext-pro/text-to-image API

This document introduces the input and output parameters of the black-forest-labs/flux-kontext-pro/text-to-image model call API for your reference when using the interface.

Request Parameters

Request Body

Field Name	Type	Required	Default	Description
prompt	string	Required	-	Prompt words
model	string	Required	-	The model name used for this request, here it is `black-forest-labs/flux-kontext-pro/text-to-image`.
n	int	Optional	1	Number of images to generate, range 1~4
aspect_ratio	string	Optional	”1:1”	The aspect ratio of the image, formatted as “width:height”, e.g. “16:9” or “1:1”. Supported sizes: “21:9”, “16:9”, “4:3”, “3:2”, “1:1”, “2:3”, “3:4”, “9:16”, “9:21”
seed	int	Optional	-1	Random seed to control the randomness of the model’s generated content. If you want the generated content to remain consistent, you can use the same seed parameter value.
steps	int	Optional	20	Number of inferences, range 1~50
guidance_scale	float	Optional	2.5	The degree of consistency between the model output and the prompt, i.e., the degree of freedom of generated images; the larger the value, the smaller the model’s freedom, and the stronger the correlation with the user’s input prompts. Range [1, 10].
negative_prompt	string	Optional	-	Negative prompt words for specifying content that should not appear in the generated image
response_format	string	Optional	”url”	Specifies the format of the generated image returned, default is `url`, optional `b64_json`

Response Parameters

Field Name	Type	Description
created	`integer`	Unix timestamp (in seconds) of when this request was created.
data	`array`	Information of the output image, including the download URL or Base64. • When specifying the format of the generated image as url, the child field of the corresponding parameter is url; • When specifying the format of the generated image as b64_json, the child field of the corresponding parameter is b64_json. Note: The link will expire within 7 days after generation, please save the image promptly.
error	`Object`	Error information object
error.code	`string`	Error code
error.message	`string`	Error message
error.param	`string`	Request id

Example

OPENAI Compatible Interface

POST https://api.umodelverse.ai/v1/images/generations

Synchronous Request


curl --location 'https://api.umodelverse.ai/v1/images/generations' \
--header "Authorization: Bearer $MODELVERSE_API_KEY" \
--header 'Content-Type: application/json' \
--data '{
    "model": "black-forest-labs/flux-kontext-pro/text-to-image",
    "prompt": "Convert to quick pencil sketch",
    "aspect_ratio": "9:16"
}'


import os
from openai import OpenAI
 
client = OpenAI(
    base_url=os.getenv("BASE_URL", "https://api.umodelverse.ai/v1"),
    api_key=os.getenv("API_KEY", "$MODELVERSE_API_KEY")
)
 
response = client.images.generate(
    model="black-forest-labs/flux-kontext-pro/text-to-image",
    prompt="Convert to quick pencil sketch",
    extra_body={
        "aspect_ratio": "9:16"
    }
)
 
print(response.data[0].url)

Response


{
  "created": 1750667997,
  "data": [
    {
      "url": "https://xxxxx/xxxx.png",
      "b64_json": "data:image/png;base64,{image_base64_string}"
    }
  ],
  "usage": {
    "input_tokens_details": {}
  }
}


{
  "error": {
    "message": "error_message",
    "type": "error_type",
    "param": "request_id",
    "code": "error_code"
  }
}