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SegmentationState stores all the information regarding the current state of the Segmentations and SegmentationRepresentations in the library. As mentioned in the previous section we have decoupled the Segmentations and SegmentationRepresentations from each other. From a Segmentation various representations can be created (labelmap supported currently). Therefore, the state also stores segmentations and their toolGroup-specific representations separately.

An overview of the state is shown below.

Global Config

Cornerstone3DTools implements two configurations, and the consumer can set each of them individually. GlobalConfig in the state stores the global configuration for all segmentation representations in all toolGroups.

You can read more in the config on how to set each individually.


SegmentationState Stores an array of colorLUTs that are used to render the segmentation representations. Cornerstone3DTools initially adds 255 colors ([ [0,0,0,0], [221, 84, 84, 255],[77, 228, 121, 255], ... ]) as the first index of this array, and by default all segmentation representations use the first colorLUT. However, using the color API in the config you can add more colors to the global colorLUT in the state and/or change the colorLUT for a specific segmentation representation.


SegmentationState stores all the segmentations in an array. It should be noted that Segmentation and SegmentationRepresentation are two separate concepts. Each Segmentation Object inside the state, stores all the required information in order for the SegmentationRepresentation to be created.

Each segmentation object has the following properties:

segmentationId: 'segmentation1',
mainType: 'Labelmap',
activeSegmentIndex: 0,
segmentsLocked: new Set(),
label: 'segmentation1',
cachedStats: {},
representationData: {
volumeId: 'segmentation1',
geometryIds: ['contourSet1', 'contourSet2'],
  • segmentationId: a required field provided by the consumer. This is the unique identifier for the segmentation.
  • mainType: set internally, by default 'Labelmap'
  • activeSegmentIndex: the active segment index that will be used to modify the data of the segmentation by tools.
  • segmentsLocked: a set of locked segment indices which will not be modified by tools.
  • label: the label of the segmentation.
  • cachedStats: a cache of the stats of the segmentation (volume etc. - not used currently)
  • representationData: THE MOST IMPORTANT PART, this is where the data for creation of the SegmentationRepresentation is stored. For instance, in LABELMAP representation, the required information for creating the SegmentationRepresentation is a cached volumeId.

Adding Segmentations to the State

Since, Segmentation and SegmentationRepresentation are separated from each other, first, we need to add the segmentation to the state. This can be done by top level API:

import { segmentation, Enums } from '@cornerstonejs/tools';

representation: {
type: Enums.SegmentationRepresentations.Labelmap,
data: {
volumeId: segmentationId,

As seen, we add an array of segmentations to the state each including a segmentationId, and a representation which includes the type and the data that is required to create the SegmentationRepresentation.


Adding a Segmentation to the state WILL NOT render the segmentation. You should add the SegmentationRepresentations to the toolGroup that is intended to render the segmentation representation (e.g., Labelmap, etc.). We will see how below.


SegmentationDisplayTool is a Tool inside Cornerstone3DTools that is responsible for displaying the segmentation representations. From each Segmentation, a ToolGroup can create a SegmentationRepresentation and display it.

Adding a SegmentationRepresentation to a ToolGroup

Next, we need to add the SegmentationRepresentation to the ToolGroup. This can be done by using the addSegmentationRepresentation method of the Segmentation module. This way, all the viewports that are added to the ToolGroup will be updated their renderers to include the new SegmentationRepresentation.

import {
} from '@cornerstonejs/tools';

* Setup toolGroups and addViewports to them before hand

const toolGroup = ToolGroupManager.getToolGroup(toolGroupId);


await segmentation.addSegmentationRepresentations(toolGroupId, [
type: Enums.SegmentationRepresentations.Labelmap,

or if the ToolGroup is displaying the segmentation representation with a specific config, you can provide it in the last argument.

const toolGroupSpecificRepresentationConfig = {
renderInactiveSegmentations: true,
representations: {
[Enums.SegmentationRepresentations.Labelmap]: {
renderOutline: true,

await segmentation.addSegmentationRepresentations(
type: Enums.SegmentationRepresentations.Labelmap,