Skip to main content
Open WebUI is a self-hosted AI interface that supports image generation through OpenAI-compatible APIs. Since Lumenfall implements the OpenAI API specification, you can use it as a drop-in image generation backend for Open WebUI. Once configured, users can generate images directly in their chat conversations - either by toggling image generation mode or through native function calling if supported by their language model.

​
Prerequisites

​
Setup

​
1. Open the image settings

In Open WebUI, navigate to Admin Panel > Settings > Images.

​
2. Enable image generation

Toggle Image Generation to on.

​
3. Configure the engine

Set the Image Generation Engine dropdown to Default (Open AI).

​
4. Set the API base URL

In the API Base URL field, enter: 
https://api.lumenfall.ai/openai/v1

​
5. Enter your API key

Paste your Lumenfall API key in the API Key field.

​
6. Leave API version blank

The API Version field is for Azure OpenAI only. Leave it empty.

​
7. Select a model

In the Model field, enter the model you want to use. For example:
  • gemini-3-pro-image
  • gpt-image-1.5
  • flux.2-max
See the full list of available models in the model catalog.

​
8. Set the image size

In the Image Size field, enter the desired dimensions. For example:
  • 1024x1024
  • 1536x1024
  • 1024x1536
Supported sizes depend on the model. See the API Reference for model-specific size options. If you’re unsure, 1024x1024 works with most models.

​
9. Save

Click Save at the bottom of the page. Open WebUI Admin Panel - Configured with Lumenfall

​
Generating images

Once configured, there are two ways to generate images in Open WebUI:

​
Image generation mode

Toggle the Image Generation switch in the chat input area, type your prompt, and send. The generated image appears directly in the chat.

​
Native function calling

If your language model supports native function calling, you can simply ask it to generate an image in natural language - for example, “Generate an image of a capybara relaxing in a hot spring.” The model will invoke the image generation tool automatically. Open WebUI - Image generated with Lumenfall

​
Image editing

Open WebUI also supports image editing. To use Lumenfall for image editing:
  1. In the same Admin Panel > Settings > Images page, scroll to the Edit Image section
  2. Toggle Image Edit to on
  3. Set the Image Edit Engine to Default (Open AI)
  4. Enter the same API base URL: https://api.lumenfall.ai/openai/v1
  5. Enter your Lumenfall API key
  6. Choose a model that supports editing (e.g. gpt-image-1.5)
  7. Click Save
Open WebUI - Image editing with Lumenfall

​
Environment variables

You can also configure Lumenfall as the image generation backend using environment variables when deploying Open WebUI: 
ENABLE_IMAGE_GENERATION=true
IMAGE_GENERATION_ENGINE=openai
IMAGES_OPENAI_API_BASE_URL=https://api.lumenfall.ai/openai/v1
IMAGES_OPENAI_API_KEY=lmnfl_your_api_key
IMAGE_GENERATION_MODEL=gemini-3-pro-image
IMAGE_SIZE=1024x1024

​
Next steps

Available models

Explore all available image generation models.

API Reference

Explore the full API documentation.