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# description: Adding Layers to an Enabled Element allows Cornerstone to display labels maps and perform image fusion.
# Enabled Element Layers
Adding Layers to an Enabled Element allows Cornerstone to display labels maps and perform image fusion.
The Enabled Element Layers API allows developers to add build a composite set of images with Cornerstone.
Basics:
- An Enabled Element can have more than one Layer.
- Each Layer is similar to an Enabled Element - They each have their own Image and Viewport, off-screen rendering Canvas, etc...
- Only a single Layer can be active at a time.
- Layers have properties for visibility and opacity, and are uniquely referenced by a Layer ID.
When a Layer is Active:
- The layer's Image is available at enabledElement.image
- The layer's Viewport is available at enabledElement.viewport
This means that typical functions such as setViewport and getViewport apply to the active layer.
Layers can be:
- Added (addLayer)
- Retrieved individually by Layer ID: getLayer
- Removed individually by Layer ID: removeLayer
Additional functions:
- The current active layer can be retrieved getActiveLayer
- The Array of all layers can be retrieved: getLayers
- The Array of all visible layers can be retrieved: getVisibleLayers