black-forest-labs/flux-kontext-pro API

This document introduces the input and output parameters for calling the black-forest-labs/flux-kontext-pro model API, allowing you to refer to the field meanings when using the interface.

Request Parameters

Request Body

Field Name	Type	Required	Default	Description
prompt	string	Conditional Required	-	Prompt
model	string	Required	-	The model name used for this request, which is `black-forest-labs/flux-kontext-pro`.
image	string	Required	-	Base64 data or image link http://xxx
n	int	Optional	1	Number of generated images, the range is 1~4
strength	float	Optional	0.8	Degree of reference to the transformed image, the range is 0~1
seed	int	Optional	-1	Random seed used to control the randomness of the model’s output. If you want the output to be consistent, use the same seed parameter value.
steps	int	Optional	20	Number of inference steps, the range is 1~50
guidance_scale	float	Optional	2.5	Degree of consistency between the model’s output and the prompt, or the degree of freedom in generated images; the larger the value, the less freedom the model has, and the stronger the relevance with the user’s input prompt. Value range [1, 20].
negative_prompt	string	Optional	-	Negative prompt, used to specify content you don’t want to appear in the generated image
response_format	string	Optional	”url”	Specifies the format to return the generated image, default is `url`, optional `b64_json`

Response Parameters

Field Name	Type	Description
created	`integer`	The Unix timestamp (seconds) for when the request was created.
data	`array`	Information about the output image, including the image download URL or Base64. • When the specified format is url, the subfield is url; • When the specified format is b64_json, the subfield is b64_json. Note: The link will expire within 7 days after generation, please be sure to save the image in time.
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",
    "prompt": "Convert to quick pencil sketch",
    "image": "data:image/png;base64,{image_base64_string}"
}'


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",
    prompt="Convert to quick pencil sketch",
    extra_body={
        "image": "data:image/png;base64,{image_base64_string}"
    }
)
 
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"
  }
}