# black-forest-labs/flux.1-dev API
This document describes the input and output parameters of the `black-forest-labs/flux.1-dev` model API for your reference when using the interface.
---
## Request Parameters
### Request Body
| Field Name | Type | Required | Default Value | Description |
| -------------- | ------ | -------- | ------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| prompt | string | Required | - | Prompt |
| model | string | Required | - | The name of the model used for this request, here it is `black-forest-labs/flux.1-dev`. |
| image | string | Optional | - | Base64 data or image link http://xxx |
| n | int | Optional | 1 | Number of images to generate, with a range of 1~4 |
| size | string | Optional | "1024x1024" | Resolution |
| strength | float | Optional | 0.8 | Degree to which the reference image is transformed, ranging from 0~1 |
| seed | int | Optional | -1 | Random seed used to control the randomness of the model's generated content. To keep the content consistent, use the same seed value. |
| steps | int | Optional | 20 | Number of inferences, ranging from 1~50 |
| guidance_scale | float | Optional | 2.5 | Degree of consistency between the model's output and the prompt, i.e., the freedom of generated images; the larger the value, the less freedom, and the stronger the correlation with the user's prompt.
Value range [1, 10]. |
| negative_prompt| string | Optional | - | Negative prompt used to specify content you do not want to appear in the generated image |
| response_format| string | Optional | "url" | Specifies the format in which to return the generated image, default is `url`, optional `b64_json` |
## Response Parameters
| Field Name | Type | Description |
| -------------- | --------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| created | `integer` | Unix timestamp (seconds) of this request creation time. |
| data | `array` | Output image information, including the URL or Base64 of the image.
• When specified to return the generated image format as url, the subfield of the parameter is url;
• When specified to return the generated image format as b64_json, the subfield of the parameter is b64_json.
Note: The link will expire 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
```bash
curl --location 'https://api.umodelverse.ai/v1/images/generations' \
--header "Authorization: Bearer $MODELVERSE_API_KEY" \
--header 'Content-Type: application/json' \
--data '{
"model": "black-forest-labs/flux.1-dev",
"prompt": "Convert to quick pencil sketch",
"n": 1,
"size": "1024x1024"
}'
```
```python
import os
from openai import OpenAI
client = OpenAI(
base_url=os.getenv("BASE_URL", "https://api.umodelverse.ai/v1"),
api_key=os.getenv("API_KEY", "$MODELVERSE_API_KEY")
)
response = client.images.generate(
model="black-forest-labs/flux.1-dev",
prompt="Convert to quick pencil sketch",
n=1,
size="1024x1024"
)
print(response.data[0].url)
```
### Response
```json
{
"created": 1750667997,
"data": [
{
"url": "https://xxxxx/xxxx.png",
"b64_json": "data:image/png;base64,{image_base64_string}"
}
],
"usage": {
"input_tokens_details": {}
}
}
```
```json
{
"error": {
"message": "error_message",
"type": "error_type",
"param": "request_id",
"code": "error_code"
}
}
```