Documentation

Create ROI Labels

An ROI label is a label that corresponds to a region of interest (ROI). You can define these types of ROI labels.

In this example, you define a vehicle group for labeling types of vehicles, and then create a Rectangle ROI label for a Car and a Truck. Optionally, you can use the Show ROI Labels drop-down menu to select On Hover, Always, or Never to control how the ROI label names appear during labeling. By default, the names will appear when you hover on an ROI.

Create Sublabels

A sublabel is a type of ROI label that corresponds to a parent ROI label. Each sublabel must belong to, or be a child of, a specific label defined in the ROI Labels pane. For example, in a driving scene, a vehicle label might have sublabels for headlights, license plates, or wheels.

Define a sublabel for headlights.

Sublabels can only be used with rectangular or polyline ROI labels and cannot have their own sublabels. For more details on working with sublabels, see Use Sublabels and Attributes to Label Ground Truth Data.

Create Attributes

An attribute provides further categorization of an ROI label or sublabel. Attributes specify additional information about a drawable label. For example, in a driving scene, attributes might include the type or color of a vehicle.

You can define these types of attributes.

Add an attribute for the vehicle type.

You can also add attributes to sublabels. Add an attribute for the headlight sublabel that tells whether the headlight is on.

To delete an attribute, right-click an ROI label or sublabel, and select the attribute to delete. Deleting the attribute removes attribute information from all previously created ROI label annotations.

Create Scene Labels

A scene label defines additional information for the entire scene. Use scene labels to describe conditions, such as lighting and weather, or events, such as lane changes.

Create a scene label to use in the video.

Label Ground Truth Manually

When you click the right arrow key to advance to the next frame, the ROI labels from the previous frame do not carry over. Only the sunny scene label applies to each frame, because this label was applied over the entire time interval.

Advance frame by frame and draw the label and sublabel ROIs manually. Also update the attribute information for these ROIs.

Label Ground Truth Using Automation Algorithm

To speed up the labeling process, you can use an automation algorithm within the app. You can either define your own automation algorithm, see Create Automation Algorithm for Labeling or use a built-in automation algorithm. In this example, you label the ground truth using a built-in algorithm.

After using an automation algorithm you can manually label the remaining frames with sublabel and attribute information.

To further evaluate your labels, you can view a visual summary of the labeled ground truth. From the app toolstrip, select View Label Summary. Use this summary to compare the frames, frequency of labels, and scene conditions. For more details, see View Summary of Ground Truth Labels. This summary does not support sublabels or attributes.

Data Source

DataSource is a groundTruthDataSource object containing the path to the images or video and timestamps. Display the properties of this object.

gTruth.DataSource

ans = 

groundTruthDataSource for a video file with properties

        Source: ...matlab\toolbox\vision\visiondata\visiontraffic.avi
    TimeStamps: [531×1 duration]

Label Definitions

LabelDefinitions is a table containing information about the label definitions. This table does not contain information about the labels that are drawn on the video frames. To save the label definitions in their own MAT-file, from the app toolstrip, select Save > Label Definitions. You can then import these label definitions into another app session by selecting Import Files.

Display the label definitions table. Each row contains information about an ROI label definition or a scene label definition. If you exported pixel label data, the LabelDefinitions table also includes a PixelLabelID column containing the ID numbers for each pixel label definition.

gTruth.LabelDefinitions

ans =
  3×6 table

      Name         Type        LabelColor        Group       Description     Hierarchy  
    _________    _________    ____________    ___________    ___________    ____________

    {'Car'  }    Rectangle    {1×3 double}    {'Vehicle'}    {0×0 char}     {1×1 struct}
    {'Truck'}    Rectangle    {1×3 double}    {'Vehicle'}    {0×0 char}     {0×0 double}
    {'Sunny'}    Scene        {1×3 double}    {'Weather'}    {0×0 char}     {0×0 double} 

Within LabelDefinitions, the Hierarchy column stores information about the sublabel and attribute definitions of a parent ROI label.

Display the sublabel and attribute information for the Car label.

gTruth.LabelDefinitions.Hierarchy{1}

ans = 

  struct with fields:
       numDoors: [1×1 struct]
          color: [1×1 struct]
       inMotion: [1×1 struct]
        carType: [1×1 struct]
      headlight: [1×1 struct]
           Type: Rectangle
    Description: ''

Display information about the headlight sublabel.

gTruth.LabelDefinitions.Hierarchy{1}.headlight

ans = 

  struct with fields:
           Type: Rectangle
    Description: ''
          Color: [0.5862 0.8276 0.3103]
           isOn: [1×1 struct]

Display information about the carType attribute.

gTruth.LabelDefinitions.Hierarchy{1}.carType

ans = 

  struct with fields:

      ListItems: {3×1 cell}
    Description: ''