vision.labeler.loading.CustomImageSource Class

Namespace: vision.labeler.loading
Superclasses: vision.labeler.loading.MultiSignalSource

Load signals from custom image sources into Ground Truth Labeler app

Since R2020a

Description

The vision.labeler.loading.CustomImageSource class creates an interface for loading signals from custom image data sources into the Ground Truth Labeler app. In the Add/Remove Signal dialog box of the app, when Source Type is set to Custom Image, this class controls the parameters in that dialog box.

To access this dialog box, in the app, select Import > Add Signals.

The vision.labeler.loading.CustomImageSource class is a handle class.

Creation

When you export labels from a Ground Truth Labeler app session that contains custom image sources, the exported groundTruthMultisignal object stores instances of this class in its DataSource property.

To create a CustomImageSource object programmatically, such as when programmatically creating a groundTruthMultisignal object, use the vision.labeler.loading.CustomImageSource function (described here).

Syntax

customImgSource = vision.labeler.loading.CustomImageSource

Description

customImgSource = vision.labeler.loading.CustomImageSource creates a CustomImageSource object for loading signals from custom image data sources. To specify the data source and the parameters required to load the source, use the loadSource method.

Properties

Name — Name of source type

"Custom Image" (default) | string scalar

Name of the type of source that this class loads, specified as a string scalar.

Attributes:

GetAccess	public
Constant	true
NonCopyable	true

Description — Description of class functionality

"A custom image source reader" (default) | string scalar

Description of the functionality that this class provides, specified as a string scalar.

Attributes:

GetAccess	public
Constant	true
NonCopyable	true

SourceName — Name of data source

[] (default) | string scalar

Name of the data source, specified as a string scalar. Typically, SourceName is the name of the file from which the signal is loaded.

Attributes:

GetAccess	public
SetAccess	protected

SourceParams — Parameters for loading custom image signal from data source

[] (default) | structure

Parameters for loading a custom image signal from a data source, specified as a structure.

This table describes the required and optional fields of the SourceParams structure.

Field	Description	Required or Optional
FunctionHandle	Custom reader function for reading images from the data source, specified as a function handle. In the Add/Remove Signal dialog box of the app, specify this function handle in the Custom Reader Function parameter. For details on creating a custom reader function, see Use Custom Image Source Reader for Labeling.	Required
Timestamps	Timestamps for the custom image signal, specified as a cell array containing a single duration vector of timestamps. (For data sources that contain multiple signals, the Timestamps cell array contains one duration vector per signal with timestamps that are loaded from the MATLAB® workspace.) In the Add/Remove Signal dialog box of the app, when you click the Import from Workspace button to read the timestamps from a variable in the MATLAB workspace, then the SourceParams property stores these timestamps in the Timestamps field.	Required

Attributes:

GetAccess	public
SetAccess	protected

SignalName — Names of signals in data source

[] (default) | string vector

Names of the signals that can be loaded from the data source, specified as a string vector.

Attributes:

GetAccess	public
SetAccess	protected

SignalType — Types of signals in data source

[] (default) | vector of vision.labeler.loading.SignalType enumerations

Types of the signals that can be loaded from the data source, specified as a vector of vision.labeler.loading.SignalType enumerations. Each signal listed in the SignalName property is of the type in the corresponding position of SignalType.

Attributes:

GetAccess	public
SetAccess	protected

Timestamp — Timestamps of signals in data source

[] (default) | cell array of duration vectors

Timestamps of the signals that can be loaded from the data source, specified as a cell array of duration vectors. Each signal listed in the SignalName property has the timestamps in the corresponding position of Timestamp.

Attributes:

GetAccess	public
SetAccess	protected

NumSignals — Number of signals in data source

0 (default) | integer

Number of signals that can be read from the data source, specified as a nonnegative integer. NumSignals is equal to the number of signals in the SignalName property.

Attributes:

GetAccess	public
SetAccess	public
Dependent	true
NonCopyable	true

Methods

Public Methods

customizeLoadPanel	customizeLoadPanel(sourceObj,panel) Customize the loading panel for the data source object. In the loading dialog box of the app, this method is invoked when you select the data source type from the Source Type list.
getLoadPanelData	[sourceName,sourceParams] = getLoadPanelData(sourceObj) Obtain the data needed to load the data source object currently selected in the loading panel. In the loading dialog box of the app, this method is invoked when you add a source. The method returns these outputs. sourceName is a string capturing the name of the data source object. sourceParams is a structure with fields containing the parameters required to load the data source object. Both of these outputs are passed to the loadSource method.
loadSource	loadSource(sourceObj,sourceName,sourceParams) Load a data source object into the app. In the loading dialog box of the app, this method is invoked after you add a source and the getLoadPanelData method executes successfully. This method is also invoked when you load the data source object into the MATLAB workspace. When you load the data source object, MATLAB expects that the source has the name sourceName and parameters sourceParams that are needed to load that source and read data from it.
readFrame	frame = readFrame(sourceObj,signalName,tsIndex) Read a frame of data from a signal contained in a data source object at the specified timestamp index. The index must be in the bounds of the length of the timestamps for that signal.
loadPanelChecker	loadPanelChecker Check the load panel for the loading dialog box of the app. This method opens a dialog box similar to the loading dialog box that you open from the Open menu on the app toolstrip. Use this method to preview how the customizeLoadPanel method populates the loading panel for the selected data source object. Static true

Examples

Create Custom Image Source

Specify the path to a folder containing a sequence of road images.

imageFolder = fullfile(toolboxdir('driving'),'drivingdata','roadSequence');

Store the images in an image datastore. The Ground Truth Labeler app and groundTruthMultisignal object do not natively support image datastores, so it is considered a custom image data source.

imds = imageDatastore(imageFolder);

Write a reader function, readerFcn, to read images from the datastore. The first input argument to the reader function, sourceName, is not used. The second input argument, currentTimestamp, is converted from a duration scalar to a 1-based index. This format is compatible with reading images from the datastore.

readerFcn = @(~,idx)readimage(imds,seconds(idx));

Create a custom image source. Load the source name, reader function, and first five timestamps of the datastore into the CustomImageSource object.

sourceName = imageFolder;
sourceParams = struct();
sourceParams.FunctionHandle = readerFcn;
sourceParams.Timestamps = seconds(1:5);
customImgSource = vision.labeler.loading.CustomImageSource;
loadSource(customImgSource,sourceName,sourceParams)

Read the first frame in the sequence. Display the frame.

signalName = customImgSource.SignalName;
I = readFrame(customImgSource,signalName,1);
figure
imshow(I)

Tips

• You can this class as a starting point for creating a custom data source loading class. To view the source code for this class, use this command:

  edit vision.labeler.loading.CustomImageSource

Version History

Introduced in R2020a