> ## Documentation Index
> Fetch the complete documentation index at: https://openrouter.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Markup

A transparent PNG overlay (arrows, circles, annotations) with the same dimensions as the first reference image, as a base64 data URL or HTTP(S) URL, guiding where an edit applies. Image-to-image requests only; honored by models with markup-guided editing (OpenAI gpt-image-2.6) and ignored otherwise.

## Fields

| Field | Type | Required | Description |
| - | - | - | - |
| `image_url` | [components.ImageGenerationRequestImageURL](../components/imagegenerationrequestimageurl.mdx) | ✔️ | N/A |
| `type` | [components.ImageGenerationRequestType](../components/imagegenerationrequesttype.mdx) | ✔️ | N/A |