# Overlay The `Overlay` labeling interface is designed for image projects where a base image is displayed together with one or more linked overlay layers. It allows users to inspect aligned layers in a single viewer and adjust overlay opacity in real time. {% embed url="" %} This interface is especially useful for microscopy and similar imaging workflows where one channel acts as a visual reference and additional layers need to be compared directly on top of it. ## Example: DAPI Microscope Images One typical use case is a DAPI Microscope Image project consisting of a base image and one or more linked overlay layers with adjustable opacity — useful for inspecting microscope images, comparing channels, and reviewing weak or partially overlapping structures without switching between separate files. [Overlay Sample Project on GitHub](https://github.com/supervisely-ecosystem/overlay-sample-project) ### What is DAPI Data? DAPI (4′,6-diamidino-2-phenylindole) is a fluorescent stain that binds strongly to DNA and is commonly used in microscopy to highlight cell nuclei. In practice, DAPI data usually appears as grayscale or blue-channel images where nuclei are bright and easy to localize. This makes DAPI an important reference layer for: * Detecting and counting nuclei; * Checking cell distribution and density; * Aligning and comparing other microscopy channels. ## How the Overlay Interface Helps The `Overlay` labeling interface helps users review microscopy data faster and with better visual clarity by providing: * Linked base image and overlay layers for direct visual comparison; * Adjustable overlay opacity for inspecting faint or partially overlapping structures; * Simple workspace focused on quality control, analysis, and interpretation of microscopy results. ## Interface Controls The overlay panel includes the following controls: * **Opacity slider** — changes overlay transparency for clearer comparison with the base image. * **Scale mode dropdown** — selects how the overlay is fitted to the viewer area. * **Preserve aspect ratio toggle** — keeps the original image proportions during scaling. * **Overlay layer preview / selector** — shows the active overlay and allows quick switching between linked overlays. ![](/files/61KJwUpuCGPHOaQai3ea) ## Working with Multiple Overlays The `Overlay` interface supports **any number of overlay layers** for each base image. This is particularly useful when working with multi-channel microscopy data or comparing multiple imaging modalities. ### Managing Multiple Overlays * **Switching between overlays**: Use the overlay layer selector to switch between different overlay layers linked to the current base image. * **Layer visibility**: Only one overlay can be displayed at a time, but you can quickly toggle between them to compare different channels or imaging modes. * **Individual opacity control**: Each overlay can have its own opacity setting adjusted via the opacity slider when that overlay is active. ![Multiple Overlays](/files/r6X8J8ThBPAXmoR5fi14) This makes it easy to inspect multiple data sources aligned to the same base image without leaving the labeling workspace or switching between separate projects. ## Geospatial Use Case: Elevation Overlay on Satellite Imagery Overlay is also effective for geospatial workflows where the DTM elevation layer is rendered directly on top of a satellite image. This setup allows annotators to tune transparency in real time and quickly validate terrain-related structures in a single scene. Instead of switching between separate files, teams can interpret optical texture and elevation signal together, which is useful for refining boundaries and resolving ambiguous areas. For the complete geospatial pipeline, see [Geospatial Data Annotation](/use-cases/geospatial/geospatial-data.md), where Overlay and MultiView are used together with downloader and export tools. ## Getting Started To start working with the `Overlay` labeling interface: 1. Create a `Images` project. 2. Select the `Overlay` labeling interface in project settings or during project creation. 3. Upload the base images together with their linked overlay layers. 4. Open the dataset in the labeling toolbox and use the overlay controls to compare layers. The standard image annotation workflow remains available, while the overlay panel adds a dedicated way to inspect linked layers in the same scene. You can also open and explore a sample [Overlay](https://app.supervisely.com/ecosystem/projects/overlay-sample-project?id=452) project in Supervisely to see how this interface works in practice. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.supervisely.com/labeling/labeling-toolbox/overlay.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. 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