encantar-js/docs/api/image-tracker.md

ImageTracker

A tracker that tracks images in a video. Images are tracked using templates known as reference images.

!!! tip “Guidelines for Images”

Read [Guidelines for Images](../guidelines-for-images.md) for tips on how to design images that are suitable for tracking.

Instantiation

AR.Tracker.Image

AR.Tracker.Image(options: object): ImageTracker

Instantiate an image tracker with the specified options.

Since: 0.4.0

Arguments

• options: object, optional. An object with the following keys (all are optional):
  • resolution: Resolution. The resolution of the tracker. Make sure that the resolution of the video is at least as high as this. Suggested values: "sm", "sm+", "md", "md+".

Returns

A new image tracker.

Example

const imageTracker = AR.Tracker.Image({
    resolution: "sm"
});

AR.Tracker.ImageTracker

AR.Tracker.ImageTracker(): ImageTracker

Instantiate an image tracker with the default settings.

Deprecated since: 0.4.0. Use AR.Tracker.Image() instead.

Returns

A new image tracker.

Properties

type

tracker.type: string, read-only

The string "image-tracker".

state

tracker.state: string, read-only

The current state of the tracker.

database

tracker.database: ReferenceImageDatabase, read-only

A database of reference images.

resolution

tracker.resolution: Resolution, read-only

The resolution adopted by the computer vision algorithms implemented in the tracker. Higher resolutions improve the tracking quality, but are computationally more expensive. Note that this resolution is different from, and should not be larger than, the resolution of the camera!

Note: this property is read-only since 0.4.0. Set the resolution when instantiating the tracker.

Events

An ImageTracker is an AREventTarget. You can listen to the following events:

targetfound

A target has been found.

Properties

• referenceImage: ReferenceImage. The reference image that is linked to the target.

Example

tracker.addEventListener('targetfound', event => {
    console.log('Found target: ' + event.referenceImage.name);
});

targetlost

A target has been lost.

Properties

• referenceImage: ReferenceImage. The reference image that is linked to the target.