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

This document introduces the input and output parameters for invoking the black-forest-labs/flux-kontext-max model API, providing a reference for understanding the meaning of fields when using the interface.

Request Parameters

Request Body

Field Name	Type	Required	Default	Description
prompt	string	Conditionally Required	-	Prompt
model	string	Required	-	The name of the model used for this request, which in this case is `black-forest-labs/flux-kontext-max`.
image	string	Required	-	Base64 data or image link http://xxx
n	int	Optional	1	Number of images to generate, with a range of 1~4
strength	float	Optional	0.8	Degree to which the reference image is transformed, with a range of 0~1
seed	int	Optional	-1	Random seed for controlling the randomness of model generation. For consistent outputs, use the same seed value.
steps	int	Optional	20	Number of inferences, with a range of 1~50
guidance_scale	float	Optional	2.5	The degree to which the model output conforms to the prompt, i.e., the freedom of image generation; the larger the value, the less freedom the model has, and the more closely it is related to the user’s input prompt. [1, 10].
negative_prompt	string	Optional	-	Negative prompt for specifying content not desired in generated images
response_format	string	Optional	”url”	Specifies the format in which generated images are returned, default is `url`, can also be `b64_json`.

Response Parameters

Field Name	Type	Description
created	`integer`	Unix timestamp (seconds) when the request was created.
data	`array`	Information about output images, including image download URL or Base64. • When the specified format for the generated image is URL, the subfield is URL; • When the format is b64_json, the subfield is b64_json. Note: The link will expire 7 days after generation, please make sure to save the image in a timely manner.
error	`Object`	Error message 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-max",
    "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-max",
    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"
  }
}